Inflammation — MCQs

Q: A 3-year-old boy is brought to the physician for follow-up examination 5 days after sustaining a forehead laceration. Examination shows a linear, well-approximated laceration over the right temple. The wound is clean and dry with no exudate. There is a small amount of pink granulation tissue present. Microscopic examination of the wound is most likely to show which of the following?

Angiogenesis with type III collagen deposition. ***Angiogenesis with type III collagen deposition*** - Five days post-laceration, the wound is in the **proliferative phase** of healing, characterized by the formation of **granulation tissue**. - **Granulation tissue** consists of new blood vessels (**angiogenesis**) and proliferating fibroblasts that deposit **type III collagen** (which is later replaced by type I collagen). *Macrophage infiltration and fibrin clot degradation* - This describes events characteristic of the **inflammatory phase** (24-48 hours post-injury), where macrophages clean up debris and the initial fibrin clot. - While some macrophages may still be present, the dominant microscopic feature at 5 days would be granulation tissue formation. *Fibroblast hyperplasia with disorganized collagen deposition* - Fibroblast proliferation and collagen deposition are indeed key features of the proliferative phase. However, specifying "disorganized collagen deposition" is somewhat less precise than angiogenesis and type III collagen, and **type III collagen** is characteristic of early granulation tissue rather than just general disorganized collagen. - This option doesn't fully capture the active angiogenesis component which is prominent in granulation tissue. *Capillary dilation with neutrophilic migration* - This is characteristic of the **acute inflammatory response** occurring within the first 24-48 hours after injury. - By day 5, neutrophils have largely been replaced by macrophages, and the inflammatory phase is transitioning into the proliferative phase. *Acellular tissue with type I collagen deposition* - **Type I collagen** deposition and scar maturation (leading to a more acellular tissue) occur much later, during the **remodeling phase** of wound healing, typically weeks to months after the injury. - At 5 days, the tissue is highly cellular and vascular.

Q: A 36-year-old woman presents with thyroid swelling. She has been healthy until now and follows all the healthcare precautions except for missing a flu shot this year. On physical examination, the thyroid gland is diffusely enlarged and tender to palpation. Laboratory findings show a decreased serum TSH level and elevated erythrocyte sedimentation rate. Which of the following histopathologic findings would most likely be found in the thyroid gland of this patient?

Mixed cellular infiltration with multinuclear giant cells. ***Mixed cellular infiltration with multinuclear giant cells*** - The patient's symptoms of a **diffusely enlarged and tender thyroid**, suppressed **TSH**, elevated **ESR**, and a recent viral illness (missing flu shot) are classic for **subacute granulomatous (De Quervain's) thyroiditis**. - Histopathologically, this condition is characterized by a **disruptive inflammatory infiltrate** with **multinucleated giant cells** engulfing colloid, surrounded by granulomatous inflammation. *Extensive fibrosis of the stroma* - This finding is characteristic of **Riedel's thyroiditis**, a rare form of chronic thyroiditis. - Riedel's thyroiditis typically presents as a **hard, fixed, and painless goiter**, often leading to compressive symptoms, which does not match this patient's tender goiter. *Lymphocytic infiltration with germinal centers* - This pattern is typical of **Hashimoto's thyroiditis**, an **autoimmune thyroid disease**. - Hashimoto's usually presents with a **painless goiter** and often leads to **hypothyroidism**, not the tender, hyperthyroid-like state seen here. *Orphan Annie nuclei with psammoma bodies* - These are hallmark features associated with **papillary thyroid carcinoma**. - This patient's acute presentation with **tenderness, inflammation**, and temporary hyperthyroidism is inconsistent with a malignant thyroid neoplasm. *Sheets of polygonal cells in amyloid stroma* - This describes the histopathology of **medullary thyroid carcinoma**. - Medullary thyroid carcinoma arises from parafollicular C-cells and is characterized by the production of **calcitonin** and often has a genetic predisposition, which is not suggested by the patient's presentation.

A 42-year-old man who recently immigrated from Mexico presents to the clinic with fever, a productive cough streaked with blood, back pain, and night sweats. He was found to be HIV-positive 3 years ago but does not know his most recent CD4+ count. With further questioning, the patient notes that he had previously experienced these symptoms when he was in Mexico, but he has no recollection of taking any treatment. Which of the following characteristics would best describe the histology of a lung biopsy specimen obtained from this patient?

A 48-year-old man comes to the physician because of a 2-day history of fever, flank pain, and hematuria. He has chronic back pain, for which he has been taking meloxicam for the past 2 weeks. His temperature is 38.9°C (102°F). Physical examination shows a diffuse maculopapular rash over his trunk and extremities. Urinalysis shows 10–15 RBC/hpf, 20 WBC/hpf, and numerous eosinophils. Histologic examination of a kidney biopsy specimen is most likely to show which of the following findings?

A 3-year-old boy is brought to the physician for follow-up examination 5 days after sustaining a forehead laceration. Examination shows a linear, well-approximated laceration over the right temple. The wound is clean and dry with no exudate. There is a small amount of pink granulation tissue present. Microscopic examination of the wound is most likely to show which of the following?

A 9-year-old boy is brought to the hospital by his mother with complaints of fever and right flank pain for the past 3 days. His mom mentions that he has had these symptoms recurrently for the past 4 years. He was treated with antibiotics in the past and got better, but eventually, these symptoms recurred. On physical examination, he is warm to touch and there is tenderness over his right costovertebral angle. The vital signs include a blood pressure of 100/64 mm Hg, a pulse of 100/min, a temperature of 38.0°C (100.4°F), and a respiratory rate of 14/min. Complete blood count results are as follows: Hemoglobin 12 g/dL Red blood cell 5.1 million cells/µL Hematocrit 45% Total leukocyte count 8,500 cells/µL Neutrophils 71% Lymphocyte 24% Monocytes 4% Eosinophil 1% Basophils 0% Platelets 240,000 cells/µL Urinalysis results: pH 6.2 Color turbid yellow RBC none WBC 8–10/HPF Protein trace Cast WBC casts Glucose absent Crystal none Ketone absent Nitrite positive A computed tomography scan shows renal scarring and multiple atrophy sites with compensatory hypertrophy of residual normal tissue. There is additional renal cortical thinning. Which of the following would be the most likely microscopic finding if a renal biopsy were to be done?

A 60-year-old man comes to the office because of an 8-month history of cough, night sweats, shortness of breath, and fatigue. He has also had a 9-kg (19.8-lb) weight loss during this time. He appears pale. Abdominal examination shows hepatosplenomegaly. His leukocyte count is 80,000/mm3 and his leukocyte alkaline phosphatase level is increased. A peripheral blood smear shows > 82% neutrophils with band forms and immature and mature neutrophil precursors. An x-ray of the chest shows a 9-mm right hilar nodule. Which of the following is the most likely cause of this patient's laboratory findings?

A 22-year-old man presents with multiple, target-like skin lesions on his right and left upper and lower limbs. He says that the lesions appeared 4 days ago and that, over the last 24 hours, they have extended to his torso. Past medical history is significant for pruritus and pain on the left border of his lower lip 1 week ago, followed by the development of an oral ulcerative lesion. On physical examination, multiple round erythematous papules with a central blister, a pale ring of edema surrounding a dark red inflammatory zone, and an erythematous halo are noted. Mucosal surfaces are free of any ulcerative and exudative lesions. Which of the following statements best explains the pathogenesis underlying this patient’s condition?

A 68-year-old woman with osteoarthritis comes to the physician because of a swollen and painful right knee for the past 2 days. Temperature is 37°C (98.6°F). Examination shows erythema and swelling of the right knee with a normal range of motion. An x-ray of the right knee shows punctate radiodensities in both menisci and in the joint capsule. Arthrocentesis of the right knee joint yields 5 mL of cloudy fluid with a leukocyte count of 27,000/mm3. Which of the following is the most likely underlying mechanism of this patient's knee pain?

A 36-year-old woman presents with thyroid swelling. She has been healthy until now and follows all the healthcare precautions except for missing a flu shot this year. On physical examination, the thyroid gland is diffusely enlarged and tender to palpation. Laboratory findings show a decreased serum TSH level and elevated erythrocyte sedimentation rate. Which of the following histopathologic findings would most likely be found in the thyroid gland of this patient?

A 32-year-old woman presents to her primary care provider complaining of a psoriatic flare that has worsened over the past 2 days. The patient states that her psoriasis is normally well-controlled. She also complains of some fatigue and states that she has recently developed pain and tenderness in the joints of her hands with the right hand being more tender than the left. Her hands are stiff in the morning, and sometimes her fingers swell up. She attributes these changes to her new job where she constantly uses her hands to manufacture cabinets. Physical exam reveals plaques with silvery scale on her elbows and knees. The distal joints of her right hand are mildly swollen and the nails on both hands appear pitted. What is the most likely pathogenesis of her joint pain?

Q10

A 37-year-old man presents to his primary care physician because he has had constipation for the last several weeks. He has also been feeling lethargic and complains that this winter has been particularly cold. He also complains that he has been gaining weight despite no change in his normal activities. He reveals that two months prior to presentation he had what felt like the flu for which he took Tylenol and did not seek medical attention. Several days after this he developed anterior neck pain. Which of the following findings would most likely be seen on biopsy of this patient's abnormality?

Inflammation US Medical PG Practice Questions and MCQs

Question 1: A 42-year-old man who recently immigrated from Mexico presents to the clinic with fever, a productive cough streaked with blood, back pain, and night sweats. He was found to be HIV-positive 3 years ago but does not know his most recent CD4+ count. With further questioning, the patient notes that he had previously experienced these symptoms when he was in Mexico, but he has no recollection of taking any treatment. Which of the following characteristics would best describe the histology of a lung biopsy specimen obtained from this patient?

A. Cells with increased nuclear-to-cytoplasmic ratio
B. Noncaseating granuloma
C. Cellular debris and macrophages followed by cystic spaces and cavitation
D. Macrophage filled with fungal microorganisms
E. Epithelioid cells with caseous necrosis surrounded by multinucleated giant cells and lymphocytes (Correct Answer)

Explanation: ***Epithelioid cells surrounded by multinucleated giant cells and lymphocytes*** - The patient's symptoms (fever, productive cough with hemoptysis, back pain, night sweats, HIV-positive status, and history of similar symptoms in Mexico) are highly suggestive of **reactivation tuberculosis (TB)**. - The characteristic histological finding in **tuberculosis** is **caseating granulomas**, which are composed of epithelioid cells (activated macrophages) surrounded by lymphocytes and multinucleated giant cells (Langhans giant cells), with a central area of **caseous necrosis**. *Cells with increased nuclear-to-cytoplasmic ratio* - This description is typical of **malignant cells**, such as those seen in carcinoma, which is not the primary presentation given the historical and symptomatic context pointing towards infection. - While lung cancer could cause some of these symptoms, the history of previous episodes and HIV points more strongly to an infectious etiology like TB. *Noncaseating granuloma* - **Noncaseating granulomas** are characteristic of diseases like **sarcoidosis** or **Crohn's disease**, which typically do not present with the described constitutional symptoms (e.g., night sweats) and hemoptysis in this context, especially with a history of HIV and prior infection. - The presence of caseous necrosis is a key differentiator for tuberculosis granulomas. *Cellular debris and macrophages followed by cystic spaces and cavitation* - This describes the histological features of a **lung abscess** or extensive tissue destruction, which can be a complication of TB but is not the primary defining characteristic of the initial granuloma formation. - While TB can lead to cavitation, the initial and most specific histological feature in active TB is the granulomatous inflammation. *Macrophage filled with fungal microorganisms* - This finding would suggest a **fungal infection** such as histoplasmosis or cryptococcosis, which can occur in HIV-positive individuals and present with similar symptoms. - However, the strong clinical picture of prior similar illness in Mexico (an endemic area for TB), systemic symptoms, and hemoptysis, makes TB a more probable diagnosis, which is characterized by granulomas rather than direct macrophage colonization by fungi.

Question 2: A 48-year-old man comes to the physician because of a 2-day history of fever, flank pain, and hematuria. He has chronic back pain, for which he has been taking meloxicam for the past 2 weeks. His temperature is 38.9°C (102°F). Physical examination shows a diffuse maculopapular rash over his trunk and extremities. Urinalysis shows 10–15 RBC/hpf, 20 WBC/hpf, and numerous eosinophils. Histologic examination of a kidney biopsy specimen is most likely to show which of the following findings?

A. Interstitial T-cell infiltration (Correct Answer)
B. Cortical cyst formation
C. Glomerular crescent formation
D. Mesangial IgA deposition
E. Papillary necrosis

Explanation: ***Interstitial T-cell infiltration*** - This patient's presentation with **fever**, **rash**, **eosinophiluria**, and acute kidney injury following meloxicam use is highly characteristic of **acute interstitial nephritis (AIN)**. - AIN is a **type IV hypersensitivity reaction** characterized by inflammation and edema of the renal interstitium, with a predominant infiltrate of **T lymphocytes and eosinophils**. *Cortical cyst formation* - **Cortical cysts** are typically associated with **polycystic kidney disease**, which is a genetic disorder presenting with multiple cysts in the renal cortex and medulla, often leading to progressive renal failure over time. - This condition does not explain the acute onset of **fever, rash, eosinophilia**, and acute kidney injury seen in this patient. *Glomerular crescent formation* - **Glomerular crescent formation** is characteristic of **rapidly progressive glomerulonephritis (RPGN)**, indicating severe glomerular injury often due to autoimmune diseases like **Goodpasture syndrome**, vasculitis, or lupus. - While RPGN can present with **hematuria** and acute kidney injury, the presence of **rash, fever**, and especially **eosinophiluria** strongly points away from a primary glomerular disease and towards an interstitial process. *Mesangial IgA deposition* - **Mesangial IgA deposition** is the hallmark of **IgA nephropathy (Berger's disease)**, which typically presents with recurrent episodes of gross or microscopic hematuria, often triggered by an infection. - It does not usually involve **fever, rash, or significant eosinophilia**, and the acute kidney injury in this case is more indicative of an allergic drug reaction. *Papillary necrosis* - **Papillary necrosis** is commonly associated with chronic analgesic abuse (**NSAID use**), **sickle cell disease**, or **diabetes mellitus**. - While the patient is taking meloxicam, the acute presentation with **fever, rash**, and prominent **eosinophiluria** is a stronger indicator of allergic interstitial nephritis rather than papillary necrosis, which usually presents with chronic pain and hematuria, often with sloughed papillae in the urine.

Question 3: A 3-year-old boy is brought to the physician for follow-up examination 5 days after sustaining a forehead laceration. Examination shows a linear, well-approximated laceration over the right temple. The wound is clean and dry with no exudate. There is a small amount of pink granulation tissue present. Microscopic examination of the wound is most likely to show which of the following?

A. Angiogenesis with type III collagen deposition (Correct Answer)
B. Macrophage infiltration and fibrin clot degradation
C. Fibroblast hyperplasia with disorganized collagen deposition
D. Capillary dilation with neutrophilic migration
E. Acellular tissue with type I collagen deposition

Explanation: ***Angiogenesis with type III collagen deposition*** - Five days post-laceration, the wound is in the **proliferative phase** of healing, characterized by the formation of **granulation tissue**. - **Granulation tissue** consists of new blood vessels (**angiogenesis**) and proliferating fibroblasts that deposit **type III collagen** (which is later replaced by type I collagen). *Macrophage infiltration and fibrin clot degradation* - This describes events characteristic of the **inflammatory phase** (24-48 hours post-injury), where macrophages clean up debris and the initial fibrin clot. - While some macrophages may still be present, the dominant microscopic feature at 5 days would be granulation tissue formation. *Fibroblast hyperplasia with disorganized collagen deposition* - Fibroblast proliferation and collagen deposition are indeed key features of the proliferative phase. However, specifying "disorganized collagen deposition" is somewhat less precise than angiogenesis and type III collagen, and **type III collagen** is characteristic of early granulation tissue rather than just general disorganized collagen. - This option doesn't fully capture the active angiogenesis component which is prominent in granulation tissue. *Capillary dilation with neutrophilic migration* - This is characteristic of the **acute inflammatory response** occurring within the first 24-48 hours after injury. - By day 5, neutrophils have largely been replaced by macrophages, and the inflammatory phase is transitioning into the proliferative phase. *Acellular tissue with type I collagen deposition* - **Type I collagen** deposition and scar maturation (leading to a more acellular tissue) occur much later, during the **remodeling phase** of wound healing, typically weeks to months after the injury. - At 5 days, the tissue is highly cellular and vascular.

Question 4: A 9-year-old boy is brought to the hospital by his mother with complaints of fever and right flank pain for the past 3 days. His mom mentions that he has had these symptoms recurrently for the past 4 years. He was treated with antibiotics in the past and got better, but eventually, these symptoms recurred. On physical examination, he is warm to touch and there is tenderness over his right costovertebral angle. The vital signs include a blood pressure of 100/64 mm Hg, a pulse of 100/min, a temperature of 38.0°C (100.4°F), and a respiratory rate of 14/min. Complete blood count results are as follows: Hemoglobin 12 g/dL Red blood cell 5.1 million cells/µL Hematocrit 45% Total leukocyte count 8,500 cells/µL Neutrophils 71% Lymphocyte 24% Monocytes 4% Eosinophil 1% Basophils 0% Platelets 240,000 cells/µL Urinalysis results: pH 6.2 Color turbid yellow RBC none WBC 8–10/HPF Protein trace Cast WBC casts Glucose absent Crystal none Ketone absent Nitrite positive A computed tomography scan shows renal scarring and multiple atrophy sites with compensatory hypertrophy of residual normal tissue. There is additional renal cortical thinning. Which of the following would be the most likely microscopic finding if a renal biopsy were to be done?

A. Sloughed tubular cells within tubular lumen
B. Segmental sclerosis and hyalinosis
C. Chronic interstitial inflammation with tubular atrophy and fibrosis (Correct Answer)
D. Tubules containing eosinophilic casts
E. Normal glomeruli with accumulated lipid in proximal convoluted tubular cells

Explanation: ***Chronic interstitial inflammation with tubular atrophy and fibrosis*** - The patient's history of recurrent fevers, flank pain, positive nitrites, WBCs, and WBC casts in urine, along with CT findings of renal scarring and atrophy, points towards **chronic pyelonephritis**. - The hallmark microscopic findings of chronic pyelonephritis include **chronic interstitial inflammation** (lymphocytes and plasma cells infiltrating the interstitium), **tubular atrophy**, and **interstitial fibrosis**. - These findings reflect the long-standing inflammatory process and structural damage characteristic of this condition. *Tubules containing eosinophilic casts* - This describes **thyroidization of tubules**, which is indeed seen in chronic pyelonephritis when dilated tubules become filled with eosinophilic colloid-like material. - While this is a characteristic finding, it is more specific but less comprehensive than the broader description of chronic interstitial inflammation with tubular atrophy and fibrosis, which encompasses the fundamental pathologic process. *Sloughed tubular cells within tubular lumen* - This finding is characteristic of **acute tubular necrosis (ATN)**, typically seen in ischemic or nephrotoxic injury. - The patient's presentation with recurrent infections and chronic structural changes is not consistent with ATN. *Normal glomeruli with accumulated lipid in proximal convoluted tubular cells* - This description is characteristic of **minimal change disease (lipoid nephrosis)**, a cause of nephrotic syndrome with heavy proteinuria and edema. - The clinical picture of recurrent infections, flank pain, and localized scarring does not align with minimal change disease. *Segmental sclerosis and hyalinosis* - These findings are typical of **focal segmental glomerulosclerosis (FSGS)**, a glomerular disease often presenting with nephrotic syndrome. - The recurrent infections and localized renal scarring with preserved glomerular function are not consistent with FSGS.

Question 5: A 60-year-old man comes to the office because of an 8-month history of cough, night sweats, shortness of breath, and fatigue. He has also had a 9-kg (19.8-lb) weight loss during this time. He appears pale. Abdominal examination shows hepatosplenomegaly. His leukocyte count is 80,000/mm3 and his leukocyte alkaline phosphatase level is increased. A peripheral blood smear shows > 82% neutrophils with band forms and immature and mature neutrophil precursors. An x-ray of the chest shows a 9-mm right hilar nodule. Which of the following is the most likely cause of this patient's laboratory findings?

A. Sarcoidosis
B. Acute lymphoblastic leukemia
C. Leukemoid reaction (Correct Answer)
D. Tuberculosis
E. Chronic myeloid leukemia

Explanation: ***Leukemoid reaction*** - The combination of **leukocytosis** (>50,000/mm³), **immature granulocytes**, and **elevated leukocyte alkaline phosphatase (LAP) score** in the presence of an underlying inflammatory or infectious process (such as the suspected lung lesion) strongly suggests a leukemoid reaction. - A leukemoid reaction is a reactive **increase in white blood cells**, often in response to severe infection or malignancy, mimicking leukemia but distinct from it due to the high LAP score and lack of specific chromosomal translocations. *Sarcoidosis* - Sarcoidosis typically presents with **non-caseating granulomas**, often affecting the lungs and lymph nodes, but does not usually cause such a profound leukocytosis with immature forms. - While a **hilar nodule** can be seen, the described hematological findings, especially the high LAP score and pronounced neutrophilia, are not characteristic of sarcoidosis. *Acute lymphoblastic leukemia* - This condition involves a proliferation of **lymphoblasts**, not mature or immature neutrophils; therefore, the peripheral smear would show a predominance of blasts and not mature neutrophil precursors. - While it can cause leukocytosis, the specific cell types and the **elevated LAP score** (LAP is typically low in ALL) rule it out. *Tuberculosis* - Tuberculosis can cause fever, night sweats, weight loss, and lung findings, but it typically does not lead to a **leukocyte count of 80,000/mm³** with such a high proportion of immature neutrophils. - While it can cause a **leukemoid reaction**, the LAP score and specific granulocyte morphology help differentiate it from other causes, and the primary diagnosis here is the reaction itself, which would be *caused* by something like TB. *Chronic myeloid leukemia* - CML also presents with marked leukocytosis and **immature myeloid cells** but is characterized by a **low leukocyte alkaline phosphatase (LAP) score** and the presence of the **Philadelphia chromosome (BCR-ABL1 fusion gene)**, which contradicts the elevated LAP score found in this patient. - While hepatosplenomegaly and constitutional symptoms align, the LAP score is a key differentiating factor.

Question 6: A 22-year-old man presents with multiple, target-like skin lesions on his right and left upper and lower limbs. He says that the lesions appeared 4 days ago and that, over the last 24 hours, they have extended to his torso. Past medical history is significant for pruritus and pain on the left border of his lower lip 1 week ago, followed by the development of an oral ulcerative lesion. On physical examination, multiple round erythematous papules with a central blister, a pale ring of edema surrounding a dark red inflammatory zone, and an erythematous halo are noted. Mucosal surfaces are free of any ulcerative and exudative lesions. Which of the following statements best explains the pathogenesis underlying this patient’s condition?

A. Circulating anti-double-stranded DNA antibodies
B. Tumor necrosis factor (TNF) alpha production by CD4+ T cells in the skin
C. Circulating anti-desmoglein antibodies
D. IgA deposition in the papillary dermis
E. Interferon (IFN) gamma production by CD8+ T cells in the skin (Correct Answer)

Explanation: ***Interferon (IFN) gamma production by CD8+ T cells in the skin*** - This patient's presentation with **target-like skin lesions** following an oral lesion (likely **herpes simplex virus** reactivation) is characteristic of **erythema multiforme (EM)**. - EM is a **Type IV hypersensitivity reaction** mediated primarily by **CD8+ cytotoxic T cells** that infiltrate the epidermis and cause keratinocyte apoptosis. - **CD8+ T cells** produce **IFN-gamma** and use perforin/granzyme pathways to destroy virus-infected or antigen-expressing keratinocytes, leading to the distinctive target lesions. *Circulating anti-double-stranded DNA antibodies* - This is a hallmark of **Systemic Lupus Erythematosus (SLE)**, which typically presents with a **malar rash**, photosensitivity, arthritis, and organ involvement, none of which are described. - While SLE can have skin manifestations, the classic target lesions of erythema multiforme are not typical, and the preceding herpes outbreak is not directly linked to SLE. *Tumor necrosis factor (TNF) alpha production by CD4+ T cells in the skin* - While **TNF-alpha** is an important pro-inflammatory cytokine involved in many dermatological conditions, it is not the primary cytokine or cellular mechanism driving the specific immune response in **erythema multiforme**. - Conditions like **psoriasis** involve significant TNF-alpha activity from CD4+ T cells, but their clinical presentation differs significantly from target lesions. - In EM, the primary effector cells are **CD8+ T cells**, not CD4+ T cells. *Circulating anti-desmoglein antibodies* - These antibodies are characteristic of **pemphigus vulgaris**, an autoimmune blistering disease that causes **flaccid bullae** and erosions, particularly on mucosal surfaces. - The patient's lesions are described as target-like with a central blister, not flaccid bullae, and mucosal surfaces are explicitly stated to be free of lesions, ruling out pemphigus. *IgA deposition in the papillary dermis* - This finding is characteristic of **dermatitis herpetiformis**, a pruritic blistering disease associated with **celiac disease**. - The lesions in dermatitis herpetiformis are typically grouped vesicles and papules, often on extensor surfaces, rather than the target lesions seen in this patient, and are intensely pruritic with no central blister.

Question 7: A 68-year-old woman with osteoarthritis comes to the physician because of a swollen and painful right knee for the past 2 days. Temperature is 37°C (98.6°F). Examination shows erythema and swelling of the right knee with a normal range of motion. An x-ray of the right knee shows punctate radiodensities in both menisci and in the joint capsule. Arthrocentesis of the right knee joint yields 5 mL of cloudy fluid with a leukocyte count of 27,000/mm3. Which of the following is the most likely underlying mechanism of this patient's knee pain?

A. Monosodium urate crystal precipitation
B. Gram-negative diplococci infection
C. Calcium pyrophosphate dihydrate crystal deposition (Correct Answer)
D. Immune complex deposition
E. Noncaseating granuloma formation

Explanation: ***Calcium pyrophosphate dihydrate crystal deposition*** - The presence of **punctate radiodensities** in the menisci and joint capsule on X-ray is characteristic of **chondrocalcinosis**, which is strongly associated with calcium pyrophosphate dihydrate (CPPD) crystal deposition disease (pseudogout). - The acute onset of a **swollen, painful knee** with a high leukocyte count in the synovial fluid (27,000/mm³) in the context of underlying osteoarthritis is consistent with a pseudogout flare. *Monosodium urate crystal precipitation* - While gout (monosodium urate crystal precipitation) also causes acute, painful arthritis with high synovial fluid leukocyte counts, the X-ray finding of **chondrocalcinosis** is not typical. - Gout commonly presents with abrupt onset pain and swelling, often involving the **first metatarsophalangeal joint**, which is not described here. *Gram-negative diplococci infection* - A synovial leukocyte count of 27,000/mm³ falls in a range that could be seen in both inflammatory arthritis and septic arthritis, though **bacterial septic arthritis typically exceeds 50,000/mm³**. - The key feature distinguishing this case from septic arthritis is the **X-ray finding of chondrocalcinosis**, which is pathognomonic for CPPD deposition disease and not associated with infection. - Additionally, the patient is **afebrile**, which makes acute bacterial infection less likely. *Immune complex deposition* - **Immune complex deposition** can cause inflammatory arthritis (e.g., rheumatoid arthritis, lupus), but these conditions usually involve a more chronic or migratory pattern, and are not directly associated with chondrocalcinosis on X-ray. - The acute, monoarticular presentation with specific radiologic findings is less suggestive of a primary immune complex-mediated process. *Noncaseating granuloma formation* - **Noncaseating granulomas** are characteristic of conditions like sarcoidosis, which can cause arthritis, but this is usually a chronic, often polyarticular, condition. - This mechanism does not explain the acute, severe monoarticular pain and swelling with chondrocalcinosis seen in this patient.

Question 8: A 36-year-old woman presents with thyroid swelling. She has been healthy until now and follows all the healthcare precautions except for missing a flu shot this year. On physical examination, the thyroid gland is diffusely enlarged and tender to palpation. Laboratory findings show a decreased serum TSH level and elevated erythrocyte sedimentation rate. Which of the following histopathologic findings would most likely be found in the thyroid gland of this patient?

A. Extensive fibrosis of the stroma
B. Mixed cellular infiltration with multinuclear giant cells (Correct Answer)
C. Lymphocytic infiltration with germinal centers
D. Orphan Annie nuclei with psammoma bodies
E. Sheets of polygonal cells in amyloid stroma

Explanation: ***Mixed cellular infiltration with multinuclear giant cells*** - The patient's symptoms of a **diffusely enlarged and tender thyroid**, suppressed **TSH**, elevated **ESR**, and a recent viral illness (missing flu shot) are classic for **subacute granulomatous (De Quervain's) thyroiditis**. - Histopathologically, this condition is characterized by a **disruptive inflammatory infiltrate** with **multinucleated giant cells** engulfing colloid, surrounded by granulomatous inflammation. *Extensive fibrosis of the stroma* - This finding is characteristic of **Riedel's thyroiditis**, a rare form of chronic thyroiditis. - Riedel's thyroiditis typically presents as a **hard, fixed, and painless goiter**, often leading to compressive symptoms, which does not match this patient's tender goiter. *Lymphocytic infiltration with germinal centers* - This pattern is typical of **Hashimoto's thyroiditis**, an **autoimmune thyroid disease**. - Hashimoto's usually presents with a **painless goiter** and often leads to **hypothyroidism**, not the tender, hyperthyroid-like state seen here. *Orphan Annie nuclei with psammoma bodies* - These are hallmark features associated with **papillary thyroid carcinoma**. - This patient's acute presentation with **tenderness, inflammation**, and temporary hyperthyroidism is inconsistent with a malignant thyroid neoplasm. *Sheets of polygonal cells in amyloid stroma* - This describes the histopathology of **medullary thyroid carcinoma**. - Medullary thyroid carcinoma arises from parafollicular C-cells and is characterized by the production of **calcitonin** and often has a genetic predisposition, which is not suggested by the patient's presentation.

Question 9: A 32-year-old woman presents to her primary care provider complaining of a psoriatic flare that has worsened over the past 2 days. The patient states that her psoriasis is normally well-controlled. She also complains of some fatigue and states that she has recently developed pain and tenderness in the joints of her hands with the right hand being more tender than the left. Her hands are stiff in the morning, and sometimes her fingers swell up. She attributes these changes to her new job where she constantly uses her hands to manufacture cabinets. Physical exam reveals plaques with silvery scale on her elbows and knees. The distal joints of her right hand are mildly swollen and the nails on both hands appear pitted. What is the most likely pathogenesis of her joint pain?

A. Autoantibodies to the Fc portion of IgG
B. Local invasive infection of the joint space
C. Deposition of crystals in the joint space
D. Release of TNF and activation of RANKL pathway (Correct Answer)
E. Repetitive injury

Explanation: ***Release of TNF and activation of RANKL pathway*** - The patient's presentation with psoriasis, **nail pitting**, and **distal interphalangeal (DIP) joint involvement** (more tender on the right, swelling, morning stiffness) is classic for **psoriatic arthritis**. - **Psoriatic arthritis** is a seronegative spondyloarthropathy characterized by inflammation driven by cytokines like **TNF-α**, which also activates the **RANKL pathway** leading to **bone erosion** and new bone formation. *Autoantibodies to the Fc portion of IgG* - This describes **rheumatoid factor (RF)**, which is characteristic of **rheumatoid arthritis (RA)**. - While both psoriatic arthritis and RA cause joint pain and stiffness, psoriatic arthritis is typically **seronegative** for RF, and RA usually affects the **metacarpophalangeal (MCP)** and **proximal interphalangeal (PIP)** joints, sparing the DIP joints. *Local invasive infection of the joint space* - A **septic joint** would present with acute, severe pain, marked swelling, erythema, warmth, and potentially fever, which are not the primary features described here. - While infection can exacerbate inflammatory conditions, the chronic, migratory, and patterned joint involvement points away from acute bacterial infection. *Deposition of crystals in the joint space* - This mechanism is characteristic of **gout** (uric acid crystals) or **pseudogout** (calcium pyrophosphate crystals). - Crystal arthropathies typically present with severe, acute, monoarticular inflammation, which differs from the described pattern of morning stiffness, multiple joint involvement (even if asymmetric), and an underlying psoriatic flare. *Repetitive injury* - While her new job might cause some discomfort, the systemic nature of her symptoms, including a worsening **psoriatic flare**, **fatigue**, **nail pitting**, and **morning stiffness**, suggests an underlying **inflammatory arthropathy** rather than purely mechanical joint pain from overuse. - **Osteoarthritis** due to repetitive injury typically lacks the inflammatory markers like morning stiffness and associated skin/nail changes seen in this patient.

Question 10: A 37-year-old man presents to his primary care physician because he has had constipation for the last several weeks. He has also been feeling lethargic and complains that this winter has been particularly cold. He also complains that he has been gaining weight despite no change in his normal activities. He reveals that two months prior to presentation he had what felt like the flu for which he took Tylenol and did not seek medical attention. Several days after this he developed anterior neck pain. Which of the following findings would most likely be seen on biopsy of this patient's abnormality?

A. Focal hyperplasia
B. Germinal follicles
C. Scalloped clear areas
D. Fibrous tissue
E. Granulomatous inflammation (Correct Answer)

Explanation: ***Granulomatous inflammation*** - The patient's presentation with **constipation**, **lethargy**, **cold intolerance**, and **weight gain** after a flu-like illness followed by **anterior neck pain** is highly suggestive of **subacute granulomatous thyroiditis (de Quervain thyroiditis)**. - A biopsy of the thyroid in cases of de Quervain thyroiditis typically reveals **granulomatous inflammation** with scattered **giant cells** and lymphocytes, reflecting the destructive inflammatory process. *Focal hyperplasia* - **Focal hyperplasia** is characterized by an increase in the number of thyroid follicular cells and is seen in conditions like **Graves' disease** or **multinodular goiter**, particularly when the gland is overstimulated. - This finding would not be expected in subacute granulomatous thyroiditis, where the primary pathology is destruction rather than proliferation. *Germinal follicles* - **Germinal follicles** are characteristic of chronic lymphocytic thyroiditis (**Hashimoto's thyroiditis**), an autoimmune condition where the thyroid gland is infiltrated by lymphocytes, plasma cells, and macrophages. - While Hashimoto's can cause hypothyroidism, the preceding flu-like illness and acute neck pain make de Quervain thyroiditis a more likely diagnosis. *Scalloped clear areas* - **Scalloped clear areas** at the colloid-epithelial interface, also known as **colloid resorption vacuoles**, are a histological feature of **hyperactive thyroid follicles**, typically seen in conditions causing hyperthyroidism like **Graves' disease**. - The patient's symptoms of lethargy, cold intolerance, and weight gain indicate hypothyroidism, which can follow the initial hyperthyroid phase of de Quervain thyroiditis but are not indicative of active hyperfunction on biopsy at this stage. *Fibrous tissue* - An increased amount of **fibrous tissue** is characteristic of **Riedel's thyroiditis**, a rare condition characterized by dense fibrosis that replaces normal thyroid parenchyma and can extend into surrounding neck structures. - This patient's presentation with a preceding febrile illness and neck pain is not typical for Riedel's thyroiditis, which usually presents as a hard, fixed mass without an antecedent viral infection.

Question 11: A 4-year-old male is accompanied by his mother to the pediatrician. His mother reports that over the past two weeks, the child has had intermittent low grade fevers and has been more lethargic than usual. The child’s past medical history is notable for myelomeningocele complicated by lower extremity weakness as well as bowel and bladder dysfunction. He has been hospitalized multiple times at an outside facility for recurrent urinary tract infections. The child is in the 15th percentile for both height and weight. His temperature is 100.7°F (38.2°C), blood pressure is 115/70 mmHg, pulse is 115/min, and respirations are 20/min. Physical examination is notable for costovertebral angle tenderness that is worse on the right. Which of the following would most likely be found on biopsy of this patient’s kidney?

A. Replacement of renal parenchyma with foamy histiocytes
B. Tubular colloid casts with diffuse lymphoplasmacytic infiltrate (Correct Answer)
C. Diffusely necrotic papillae with dystrophic calcification
D. Mononuclear and eosinophilic infiltrate
E. Destruction of the proximal tubule and medullary thick ascending limb

Explanation: ***Tubular colloid casts with diffuse lymphoplasmacytic infiltrate*** - The patient's history of **myelomeningocele**, recurrent **urinary tract infections (UTIs)**, and current symptoms (fever, lethargy, CVA tenderness) strongly suggest **chronic pyelonephritis**. - **Chronic pyelonephritis** is characterized histologically by **tubular atrophy**, interstitial fibrosis, and a **lymphoplasmacytic infiltrate**, often with "thyroidization" of the tubules where they are dilated and filled with colloid casts. *Replacement of renal parenchyma with foamy histiocytes* - This description is characteristic of **xanthogranulomatous pyelonephritis**, a severe and rare form of chronic pyelonephritis. - While possible given chronic UTIs, the more general and common finding in chronic pyelonephritis is a diffuse lymphoplasmacytic infiltrate, not necessarily dominant foamy histiocytes. *Diffusely necrotic papillae with dystrophic calcification* - This finding is most consistent with **renal papillary necrosis**. - Renal papillary necrosis is typically associated with conditions like **analgesic nephropathy**, **sickle cell disease**, or severe acute pyelonephritis, but not the primary histological change in chronic pyelonephritis as described. *Mononuclear and eosinophilic infiltrate* - A prominent **eosinophilic infiltrate** in the kidney is often seen in **acute interstitial nephritis**, which can be drug-induced. - While chronic inflammation involves mononuclear cells, the specific mention of eosinophils makes this less likely to be the primary finding in chronic pyelonephritis from recurrent UTIs. *Destruction of the proximal tubule and medullary thick ascending limb* - Destruction of specific tubular segments, particularly the **proximal tubule**, is characteristic of acute tubular necrosis (ATN). - While chronic pyelonephritis leads to tubular atrophy and damage, the primary description here points to an acute injury rather than the chronic inflammatory changes expected.

Question 12: A 68-year-old man is admitted to the emergency department after 2 days of difficulty breathing and fever. His past medical history is significant for hypertension and benign prostate hypertrophy. He takes hydrochlorothiazide and tamsulosin. He also admits to drinking alcohol on the weekends and a half pack a day smoking habit. Upon admission, he is found to have blood pressure of 125/83 mm Hg, pulse of 88/min, a respiratory rate of 28/min, and a temperature of 38.9°C (102°F). On physical exam breath sounds are decreased at the left pulmonary base. A chest x-ray reveals consolidation in the left lower lobe. Additional laboratory tests demonstrate leukocytosis, elevated C-reactive protein, a serum creatinine (Cr) of 8.0 mg/dL, and a blood urea nitrogen (BUN) of 32 mg/dL. The patient is admitted to the hospital and started on cefepime and clarithromycin. His dyspnea slowly improves after 48 hours, however, his body temperature remains at 39°C (102.2°F). Recent laboratory tests show reduced C-reactive protein levels, a Cr of 1.8 mg/dL and a BUN of 35 mg/dL. A urinalysis is ordered. Which of the following would you expect to find in this patient’s urine?

A. Hyaline casts
B. Urate crystals
C. Acanthocytes
D. White blood cell casts (Correct Answer)
E. Calcium oxalate crystals

Explanation: ***White blood cell casts*** - This patient's **persistent fever** despite improving pneumonia symptoms and **acute kidney injury** (Cr 8.0 → 1.8 mg/dL) after starting antibiotics strongly suggests **drug-induced acute interstitial nephritis (AIN)**. - **WBC casts** are the hallmark urinary finding in **acute interstitial nephritis**, indicating inflammatory infiltration of the renal tubules and interstitium. - **Classic triad of AIN**: fever, rash (not always present), and AKI after drug exposure (cefepime and clarithromycin are known culprits). - The persistence of fever while other inflammatory markers improve points to an **allergic/hypersensitivity reaction** in the kidneys rather than worsening infection. *Hyaline casts* - **Hyaline casts** are composed of **Tamm-Horsfall protein** and are the most common type of cast, seen in concentrated urine, after exercise, or with dehydration. - They are **non-specific** and can occur in healthy individuals; they do not indicate acute inflammation or explain the persistent fever and AKI pattern. *Urate crystals* - **Urate crystals** are seen in acidic urine and associated with **hyperuricemia, gout**, or **tumor lysis syndrome**. - They do not explain the inflammatory process causing persistent fever or the temporal relationship with antibiotic initiation. *Acanthocytes* - **Acanthocytes** (dysmorphic RBCs) indicate **glomerular bleeding** and are characteristic of **glomerulonephritis**. - There is **no hematuria** mentioned in this case, and the clinical picture (fever, drug exposure, AKI) points to **tubular-interstitial disease** (AIN) rather than glomerular pathology. *Calcium oxalate crystals* - **Calcium oxalate crystals** are common urinary findings that may be associated with **nephrolithiasis, ethylene glycol toxicity**, or dietary factors. - Their presence is **non-specific** and does not explain the acute inflammatory renal process with persistent fever following antibiotic exposure.

Question 13: A 69-year-old diabetic woman comes to the emergency department due to right flank pain for 10 days. Her right flank pain is radiating towards her groin and is associated with fever and chills. The pain is exacerbated with hip extension. She feels fatigued and is lying on her left side with her right hip flexed. The CT guided percutaneous drainage reveals 900 ml of greenish pus. The vital signs include blood pressure 145/75 mm Hg, pulse rate 96/min, temperature 36.9°C (98.4°F), respiratory rate 16/min, and the oxygen saturation is 95%. The complete blood count shows the following results upon admission: CBC results Leukocytes 16,600/mm3 Neutrophils 80% Lymphocytes 16% Eosinophils 1% Basophils 1% Monocyte 2% Hemoglobin 7.6 g/dL Creatinine 0.8 mg/dL BUN 15 mg/dL Which of the following processes most likely could have occurred?

A. Neutrophil diapedesis and release of chemotactic agents (Correct Answer)
B. Decreased expression of selectin in the endothelium
C. Vasoconstriction
D. Activation of cytosolic caspases
E. Downregulation of cellular adhesion molecules in the endothelium

Explanation: ***Neutrophil diapedesis and release of chemotactic agents*** - The patient presents with symptoms and signs of a **psoas abscess**, including **flank pain radiating to the groin**, fever, chills, a **positive psoas sign** (pain with hip extension, lying with hip flexed), leukocytosis with neutrophilia, and the drainage of **greenish pus**. - This indicates an acute bacterial infection, which would involve the recruitment of **neutrophils** to the site of infection via **diapedesis** (migration through the vessel wall), guided by **chemotactic agents** (such as IL-8, C5a, and bacterial products) released during inflammation. *Downregulation of cellular adhesion molecules in the endothelium* - **Downregulation of adhesion molecules** would hinder the migration of leukocytes into the infected tissue, which contradicts the presence of a large pus collection and **neutrophilic leukocytosis**. - Effective leukocyte extravasation into inflamed tissues relies on the **upregulation** and appropriate function of these adhesion molecules. *Decreased expression of selectin in the endothelium* - **Selectins** are crucial for the initial rolling of leukocytes along the endothelial surface, a necessary step before firm adhesion and diapedesis. - **Decreased expression** would impair leukocyte recruitment, which is inconsistent with the patient's robust inflammatory response and pus formation. *Vasoconstriction* - In an inflammatory process like an abscess, the initial response generally involves **vasodilation** in the affected area, leading to increased blood flow and facilitating the delivery of immune cells and mediators. - While some localized constriction might occur in later stages or distal to the site, overall **vasodilation** is characteristic of acute inflammation. *Activation of cytosolic caspases* - **Activation of cytosolic caspases** is a hallmark of **apoptosis** (programmed cell death), which is a controlled process and not the primary mechanism behind the massive accumulation of pus and acute inflammation seen in a bacterial abscess. - While some host cells might undergo apoptosis during infection, the significant pus indicates a predominant **necrotic** and inflammatory process driven by bacterial toxins and immune cell activity.

Question 14: A 33-year-old woman presents to the emergency department with a 3-day history of backache, progressive bilateral lower limb weakness, and a pins-and-needles sensation in both of her legs. She has not passed urine for the past 24 hours. Her medical history is unremarkable. Her blood pressure is 112/74 mm Hg, heart rate is 82/min, and temperature is 37°C (98.6°F). She is alert and oriented to person, place, and time. Higher mental functions are intact. Muscle strength is 5/5 in the upper limbs and 3/5 in the lower limbs. The lower limb weakness is accompanied by increased muscle tone, brisk deep tendon reflexes, and a bilateral upgoing plantar reflex. Pinprick sensations are decreased at and below the level of the umbilicus. The bladder is palpable on abdominal examination. What is the most likely pathophysiology involved in the development of this patient’s condition?

A. Nutritional deficiency
B. Low serum potassium levels
C. Demyelination of peripheral nerves
D. Inflammation of the spinal cord (Correct Answer)
E. Enlargement of a central fluid-filled cavity within spinal cord

Explanation: ***Inflammation of the spinal cord*** - The patient presents with **rapidly progressive bilateral lower limb weakness**, **sensory deficits below the umbilicus**, and **urinary retention**, along with **upper motor neuron signs** (increased tone, brisk reflexes, upgoing plantars). This clinical picture is highly suggestive of **acute transverse myelitis**, which involves inflammation of the spinal cord. - **Acute transverse myelitis** typically involves focal inflammation that damages the myelin and/or axons of the spinal cord, leading to neurological dysfunction at and below the level of the lesion. *Nutritional deficiency* - Nutritional deficiencies, such as **Vitamin B12 deficiency**, can cause neurological symptoms, including weakness and sensory issues, but they typically develop more gradually and often present with a **peripheral neuropathy** or **subacute combined degeneration** (demyelination of posterior columns and corticospinal tracts), usually affecting vibration and proprioception more prominently. - The acute onset, prominent upper motor neuron signs, and discrete sensory level are less typical for isolated nutritional deficiencies. *Low serum potassium levels* - **Hypokalemia** can cause **muscle weakness** and paralysis, but it typically presents with **flaccid paralysis** and **decreased deep tendon reflexes**, characteristic of a lower motor neuron disorder. - The patient's presentation of **spasticity**, **brisk reflexes**, and an **upgoing plantar reflex** contradicts the hallmarks of hypokalemic paralysis. *Demyelination of peripheral nerves* - **Demyelination of peripheral nerves**, as seen in conditions like **Guillain-Barré Syndrome**, typically causes **ascending paralysis** with **areflexia** or **hyporeflexia** and sensory loss in a "stocking-glove" distribution. - The findings of **increased muscle tone**, **brisk reflexes**, and a **distinct sensory level at the umbilicus** point towards a central nervous system lesion rather than a peripheral neuropathy. *Enlargement of a central fluid-filled cavity within spinal cord* - An **enlarged central fluid-filled cavity within the spinal cord**, known as a **syrinx** or **syringomyelia**, typically causes symptoms that are more chronic and progressive. - Its classic presentation often involves **cape-like loss of pain and temperature sensation** due to damage to the spinothalamic tracts, often with dissociated sensory loss, and typically **lower motor neuron signs** at the level of the syrinx (weakness, atrophy, fasciculations) and **upper motor neuron signs** below the level of the syrinx. The acute, rapid onset and sensory level are more consistent with an acute inflammatory process.

Question 15: A 31-year-old woman scrapes her finger on an exposed nail and sustains a minor laceration. Five minutes later, her finger is red, swollen, and painful. She has no past medical history and does not take any medications. She drinks socially with her friends and does not smoke. The inflammatory cell type most likely to be prominent in this patient's finger has which of the following characteristics?

A. Segmented nuclei (Correct Answer)
B. Dramatically expanded endoplasmic reticulum
C. Large cell with amoeboid movement
D. Multiple peripheral processes
E. Dark histamine containing granules

Explanation: ***Segmented nuclei*** - This scenario describes **acute inflammation** following a minor injury, with classic signs of **redness, swelling, and pain** within minutes. - **Neutrophils** are the primary inflammatory cells in acute inflammation and are characterized by their **segmented (multi-lobed) nuclei.** *Dramatically expanded endoplasmic reticulum* - An expanded endoplasmic reticulum is characteristic of cells highly active in protein synthesis and secretion, such as **plasma cells** producing antibodies. - Plasma cells are typically involved in **chronic inflammation** and adaptive immune responses, not rapid acute inflammation. *Large cell with amoeboid movement* - This describes **macrophages**, which are phagocytic cells important in both acute and chronic inflammation, and in cleaning up debris. - While macrophages are present, **neutrophils** are the predominant early responders in acute bacterial infections and tissue injury. *Multiple peripheral processes* - This description is characteristic of **dendritic cells**, which are antigen-presenting cells that initiate adaptive immune responses. - Dendritic cells play a role in linking innate and adaptive immunity but are not the primary inflammatory cell type in the immediate acute response. *Dark histamine containing granules* - This description applies to **mast cells** and **basophils**, which release histamine and other mediators in allergic reactions and acute inflammation. - While mast cells are involved in the immediate response by releasing mediators, **neutrophils** are the main cellular players migrating to the site of injury.

Question 16: A 14-year-old boy is brought to the physician by his parents for the evaluation of a skin rash for one day. The patient reports intense itching. He was born at 39 weeks' gestation and has a history of atopic dermatitis. He attends junior high school and went on a camping trip with his school the day before yesterday. His older brother has celiac disease. Examination shows erythematous papules and vesicles that are arranged in a linear pattern on the right forearm. Laboratory studies are within normal limits. Which of the following is the most likely underlying cause of this patient's symptoms?

A. Preformed IgE antibodies
B. Immune complex formation
C. IgG antibodies against desmoglein
D. Presensitized T cells (Correct Answer)
E. IgG antibodies against hemidesmosomes

Explanation: ***Presensitized T cells*** - The patient's rash, characterized by **erythematous papules and vesicles in a linear pattern**, after a camping trip, is highly suggestive of **allergic contact dermatitis** caused by exposure to poison ivy or similar plants. - Allergic contact dermatitis is a **Type IV hypersensitivity reaction** mediated by **presensitized T cells** that recognize antigens presented by Langerhans cells in the skin upon re-exposure. *Preformed IgE antibodies* - This mechanism is characteristic of **Type I hypersensitivity reactions**, such as **anaphylaxis** or **atopic dermatitis flares** triggered by allergens binding to **IgE on mast cells**. - While the patient has a history of atopic dermatitis, the linear pattern of the rash after contact with an environmental trigger points away from an immediate IgE-mediated response. *Immune complex formation* - This describes a **Type III hypersensitivity reaction**, where **antigen-antibody complexes** deposit in tissues, leading to inflammation, as seen in conditions like **serum sickness** or **lupus nephritis**. - The clinical presentation of a linear, vesicular rash is not consistent with immune complex deposition. *IgG antibodies against desmoglein* - This mechanism is central to **pemphigus vulgaris**, an **autoimmune blistering disease** where IgG antibodies disrupt cell-cell adhesion in the epidermis. - Pemphigus vulgaris typically presents with **flaccid bullae** and erosions, usually without a clear linear pattern or acute environmental trigger. *IgG antibodies against hemidesmosomes* - This mechanism is characteristic of **bullous pemphigoid**, another **autoimmune blistering disorder** where IgG antibodies target components of the **dermal-epidermal junction**. - Bullous pemphigoid exhibits **tense bullae** and often affects older individuals, which does not match the patient's age or rash characteristics.

Question 17: A 62-year-old woman with type 2 diabetes mellitus is brought to the emergency room because of a 3-day history of fever and shaking chills. Her temperature is 39.4°C (103°F). Examination of the back shows right costovertebral angle tenderness. Analysis of the urine shows WBCs, WBC casts, and gram-negative rods. Ultrasound examination of the kidneys shows no signs of obstruction. Biopsy of the patient's kidney is most likely to show which of the following?

A. Polygonal clear cells filled with lipids and carbohydrates
B. Polymorphonuclear leukocytes in tubules (Correct Answer)
C. Tubular eosinophilic casts
D. Widespread granulomatous tissue and foamy macrophages
E. Cystic dilation of the renal medulla

Explanation: ***Polymorphonuclear leukocytes in tubules*** - The patient presents with classic signs and symptoms of **acute pyelonephritis**, including fever, chills, **costovertebral angle tenderness**, **WBCs and WBC casts** in the urine, and **gram-negative rods**, indicating a bacterial infection of the kidney parenchyma. - A kidney biopsy in acute pyelonephritis would reveal an intense **inflammatory infiltrate** primarily composed of **polymorphonuclear leukocytes (neutrophils)** within the renal tubules and interstitium, responding to the bacterial invasion. *Polygonal clear cells filled with lipids and carbohydrates* - This description is characteristic of **renal cell carcinoma**, specifically the **clear cell subtype**. - While this is a possible renal pathology, it does not align with the acute infectious presentation of fever, chills, CVA tenderness, and urinary findings of infection. *Tubular eosinophilic casts* - **Eosinophilic casts** in renal tubules are typical of **acute tubular necrosis (ATN)**, often resulting from ischemic or nephrotoxic injury. - Although ATN can cause acute renal failure, the presence of **fever, shaking chills, and gram-negative rods** points more directly to an active bacterial infection. *Widespread granulomatous tissue and foamy macrophages* - This finding is suggestive of a granulomatous disease like **tuberculosis** or **xanthogranulomatous pyelonephritis**. - While **xanthogranulomatous pyelonephritis** is a severe chronic form of pyelonephritis, it typically involves a destructive mass and often presents with a more subacute or chronic course rather than acute onset with shaking chills and evidence of uncomplicated bacterial infection. *Cystic dilation of the renal medulla* - This points to conditions such as **medullary sponge kidney** or **polycystic kidney disease**. - These are primarily congenital or developmental anomalies and do not explain the acute signs of infection and inflammation seen in this patient.

Question 18: A 40-year-old man comes to his doctor because of 2 weeks of progressively worsening pain on the outer side of his right elbow. He does not recall any trauma to the area. The patient plays tennis recreationally and has recently gone from playing weekly to playing daily in preparation for a local tournament. He has had some pain relief with ibuprofen. On physical examination, there is tenderness over the lateral surface of the right distal humerus. The pain is reproduced by supinating the forearm against resistance. Which of the following is the most likely underlying cause of this patient's condition?

A. Bursal inflammation
B. Nerve compression at the elbow
C. Repeated wrist flexion
D. Repeated wrist extension (Correct Answer)
E. Excessive stress to bone

Explanation: ***Repeated wrist extension*** - This patient's symptoms (pain on the **outer side of the elbow**, tenderness over the **lateral epicondyle**, pain with resisted **supination**) are classic for **lateral epicondylitis**, also known as **tennis elbow**. - Lateral epicondylitis is an **overuse injury** caused by repetitive microtrauma to the **extensor tendons** of the forearm, particularly the **extensor carpi radialis brevis**, which originate from the **lateral epicondyle** and are heavily involved in **wrist extension** and supination (as seen in tennis activities). *Bursal inflammation* - **Bursitis** at the elbow typically presents as swelling and tenderness over the **olecranon bursa** (posterior elbow) rather than the lateral epicondyle. - Pain is usually reproduced by direct compression of the bursa or flexion of the elbow, not specifically by resisted supination. *Nerve compression at the elbow* - **Nerve compression** at the elbow (e.g., ulnar neuropathy, radial tunnel syndrome) typically causes **neuropathic symptoms** such as numbness, tingling, or weakness in the distribution of the affected nerve. - While radial tunnel syndrome can cause pain near the lateral epicondyle, it is often described as a deeper, aching pain and does not typically involve tenderness directly over the epicondyle or pain with resisted supination in the same manner as epicondylitis. *Repeated wrist flexion* - Repeated wrist flexion is associated with **medial epicondylitis** (golfer's elbow), which causes pain on the **inner side of the elbow** and tenderness over the **medial epicondyle**. - This condition affects the **flexor-pronator mass** of the forearm, not the extensor tendons on the lateral side. *Excessive stress to bone* - While excessive stress can lead to **stress fractures**, these are less common in the elbow joint in this context and typically present with persistent, localized bone pain that worsens with activity and may show up on imaging. - The patient's specific symptoms of **tenderness at the epicondyle** and pain with resisted movement are more indicative of a soft tissue, **tendinous injury** rather than a primary bone pathology.

Question 19: A 33-year-old man with a history of IV drug and alcohol abuse presents to the emergency department with back pain. He states that his symptoms started 3 days ago and have been gradually worsening. His temperature is 102°F (38.9°C), blood pressure is 127/68 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for tenderness over the mid thoracic spine. Laboratory values are only notable for a leukocytosis and an elevated ESR and CRP. Which of the following is the most likely diagnosis?

A. Degenerative spine disease
B. Herniated nucleus pulposus
C. Musculoskeletal strain
D. Osteomyelitis (Correct Answer)
E. Spinal epidural hematoma

Explanation: ***Osteomyelitis*** - The patient's history of **IV drug abuse** is a major risk factor for **hematogenous osteomyelitis**, especially vertebral osteomyelitis. - The presence of **fever**, **localized spinal tenderness**, **leukocytosis**, and elevated **ESR** and **CRP** are classic signs of infection. *Degenerative spine disease* - This condition typically presents with **chronic pain** and insidious onset, not acute fever and inflammatory markers. - While it can cause back pain, it is not associated with systemic signs of infection or a rapid worsening course like in this case. *Herniated nucleus pulposus* - Primarily causes **radicular pain** and neurological deficits due to nerve compression, often without systemic symptoms. - There are no signs of infection, fever, or elevated inflammatory markers associated with a simple herniated disc. *Musculoskeletal strain* - This would present with localized pain, but rarely with **fever**, **leukocytosis**, and markedly elevated inflammatory markers. - It is typically a self-limiting condition with symptoms that would not progressively worsen over three days with systemic signs of infection. *Spinal epidural hematoma* - This is characterized by sudden, severe back pain and often rapid onset neurological deficits, particularly in patients on anticoagulants or with coagulopathies. - It would not typically present with **fever** and elevated inflammatory markers suggestive of an infection.

Question 20: A 48-year-old male dies in the intensive care unit following a severe Streptococcus pneumoniae pneumonia and septic shock. Autopsy of the lung reveals a red, firm left lower lobe. What would you most likely find on microscopic examination of the lung specimen?

A. Eosinophilia in the alveolar septa
B. Fragmented erythrocytes
C. Collagen whorls
D. Vascular dilation and noncaseating granulomas
E. Alveolar exudate containing neutrophils, erythrocytes, and fibrin (Correct Answer)

Explanation: ***Alveolar exudate containing neutrophils, erythrocytes, and fibrin*** - This describes the **red hepatization** stage of lobar pneumonia, which follows congestion and is characterized by a firm, red lung due to capillary congestion and extravasation of red blood cells, neutrophils, and fibrin into the alveoli. - The presence of **Streptococcus pneumoniae pneumonia** and the macroscopic finding of a **red, firm left lower lobe** are consistent with this stage of acute inflammation where inflammatory cells and plasma proteins fill the alveolar spaces. *Eosinophilia in the alveolar septa* - **Eosinophilia** in the lung is typically associated with allergic reactions, parasitic infections, or certain drug-induced lung diseases, not acute bacterial pneumonia. - The primary inflammatory cell in acute bacterial pneumonia, especially in the early stages, is the **neutrophil**. *Fragmented erythrocytes* - **Fragmented erythrocytes** (schistocytes) are typically seen in microangiopathic hemolytic anemias, such as thrombotic thrombocytopenic purpura or disseminated intravascular coagulation. - While septic shock can lead to DIC, fragmented erythrocytes are not the characteristic microscopic finding within the lung parenchyma itself for bacterial pneumonia. *Collagen whorls* - **Collagen whorls** are characteristic of conditions like silicosis, where they form within the lung parenchyma as part of a fibrotic response to inhaled silica particles. - This finding is indicative of chronic restrictive lung disease, not acute bacterial pneumonia. *Vascular dilation and noncaseating granulomas* - **Noncaseating granulomas** are the hallmark of diseases such as sarcoidosis, Crohn's disease, or foreign body reactions. - While vascular dilation can occur in inflammation, the presence of noncaseating granulomas would point away from an acute bacterial pneumonia and towards a granulomatous inflammatory process.

Question 21: A 68-year-old man is brought to the emergency department 30 minutes after the onset of uncontrollable jerking movements of his arms and legs followed by loss of consciousness. His wife says that he seemed confused this morning and had a headache. Immediately before the shaking episode, he said that he smelled rotten eggs. He is unresponsive. Cerebrospinal fluid (CSF) analysis shows a leukocyte count of 700/μL (70% lymphocytes), a glucose concentration of 60 mg/dL, and a protein concentration of 80 mg/dL. Despite appropriate lifesaving measures, the man dies. Which of the following is most likely to be found on postmortem examination of this patient?

A. Hemorrhage into the adrenal glands
B. Spore-forming, obligate anaerobic rods
C. Atrophy of the mammillary bodies
D. Cytoplasmic inclusions in cerebellar Purkinje cells
E. Necrosis of the temporal lobes (Correct Answer)

Explanation: ***Necrosis of the temporal lobes*** - The patient's symptoms (headache, confusion, seizure preceded by **olfactory aura** smelling rotten eggs) and CSF findings (**lymphocytic pleocytosis**, moderately elevated protein, normal glucose) are highly suggestive of **herpes simplex encephalitis (HSE)**. - HSE typically causes severe **necrotizing encephalitis** with a predilection for the **temporal and frontal lobes**, especially the medial temporal lobes, leading to significant **tissue necrosis**. *Hemorrhage into the adrenal glands* - This finding, known as **Waterhouse-Friderichsen syndrome**, is typically associated with **fulminant meningococcemia**, which presents with rapid onset of sepsis, petechial rash, and profound shock, not primarily with encephalitis and seizures. - The CSF analysis in meningococcemia would show **neutrophilic pleocytosis** and markedly low glucose, which differs from this patient's lymphocytic predominance and normal glucose. *Spore-forming, obligate anaerobic rods* - This describes **Clostridium** species, which are associated with conditions like **tetanus** or **botulism**, causing distinct neurological symptoms such as muscle spasms or flaccid paralysis, rather than focal seizures and encephalitis. - These bacteria are not typical causative agents for acute viral encephalitis, and their presence would not be the primary finding in a postmortem examination related to the described illness. *Atrophy of the mammillary bodies* - **Atrophy of the mammillary bodies** is characteristic of **Wernicke-Korsakoff syndrome**, a neurological disorder caused by **thiamine deficiency**, often seen in chronic alcoholics. - This syndrome presents with **ophthalmoplegia, ataxia, and confusion** (Wernicke encephalopathy) followed by memory impairment (Korsakoff psychosis), which does not align with the acute seizure and encephalitis presentation. *Cytoplasmic inclusions in cerebellar Purkinje cells* - **Cytoplasmic inclusions (Negri bodies)** are pathognomonic for **rabies encephalitis** and are classically found in **hippocampal pyramidal neurons**, though they can also occur in cerebellar Purkinje cells and cortical neurons. - Rabies typically presents with prodromal symptoms followed by acute neurological dysfunction (e.g., hydrophobia, agitation, paralysis) and rapidly progresses to coma and death, which is a different clinical course and viral etiology than suggested by the temporal lobe involvement and olfactory aura.

Question 22: A 45-year-old female is undergoing renal transplantation for management of chronic renal failure secondary to glomerulonephritis. The transplant surgeon placed the donor kidney in the recipient and anastomosed the donor renal artery to the recipient's external iliac artery as well as the donor ureter to the recipient's bladder. After removing the clamps on the external iliac artery, the recipient's blood is allowed to perfuse the transplanted kidney. Within 3 minutes, the surgeon notes that the kidney does not appear to be sufficiently perfused. Upon further investigation, an inflammatory reaction is noted that led to clotting off of the donor renal artery, preventing blood flow to the transplanted organ. Which of the following best describes the pathophysiology of this complication?

A. Type III hypersensitivity reaction
B. Type IV hypersensitivity reaction
C. Graft-versus-host disease
D. Type I hypersensitivity reaction
E. Hyperacute rejection (Correct Answer)

Explanation: ***Hyperacute rejection*** - This scenario describes **hyperacute rejection**, a **Type II hypersensitivity reaction** that occurs minutes to hours after transplantation due to pre-existing host antibodies (e.g., ABO or HLA antibodies) recognizing donor antigens on endothelial cells. - The binding of these antibodies activates the complement system, leading to rapid **antibody-mediated cytotoxicity**, **thrombosis** of the graft vasculature, and ischemic necrosis. - This represents the pathophysiologic mechanism causing the immediate graft failure observed. *Type III hypersensitivity reaction* - This reaction involves the formation of **immune complexes** (antigen-antibody complexes) that deposit in tissues, leading to inflammation. - It typically manifests hours to days after exposure and is not characterized by immediate graft thrombosis. *Type IV hypersensitivity reaction* - This is a **delayed-type hypersensitivity** mediated by T lymphocytes and macrophages, rather than antibodies. - It usually occurs days to weeks after transplantation (e.g., in acute cellular rejection) and does not cause rapid vascular occlusion. *Graft-versus-host disease* - **Graft-versus-host disease (GVHD)** occurs when immunocompetent T cells from the donor (graft) recognize recipient (host) tissues as foreign and attack them. - This complication is most common in **hematopoietic stem cell transplantation** and is unlikely to manifest minutes after solid organ transplantation. *Type I hypersensitivity reaction* - This is an immediate, **IgE-mediated allergic reaction** involving mast cell degranulation and release of inflammatory mediators. - While rapid, it typically involves systemic allergic symptoms (e.g., anaphylaxis) or localized allergic responses, not specifically graft thrombosis in this context.

Question 23: A 66-year-old farmer is being evaluated for abnormal lung findings on a low dose chest CT scan obtained as part of his lung cancer screening. He has a 50-pack-year smoking history and has been hesitant to quit. He has a non-productive cough but brushes it away saying he is not bothered by it. He denies ever coughing up blood, breathlessness, chest pain, fatigue, or weight loss. He has never sought any medical care and states that he has always been in good shape. He consumes alcohol moderately and uses marijuana occasionally. He lives with his wife and has not traveled recently. On physical examination, his temperature is 37.1°C (98.8°F), blood pressure is 148/70 mm Hg, and pulse rate is 95/min. His BMI is 32 kg/m2. A general physical examination is unremarkable. Coarse breath sounds are present bilaterally. The cardiac exam is normal. Laboratory studies show a normal complete blood count and comprehensive metabolic panel. A follow-up high-resolution CT scan is performed that shows small irregular subcentimeter pulmonary nodules, several of which are cavitated in both lungs, predominantly distributed in the upper and middle zones. There is no mediastinal or hilar lymphadenopathy. A transbronchial needle aspiration of the lesion is performed which shows a nodular pattern of abundant, granular, mildly eosinophilic cells with grooved nuclei with indented nuclear membranes and a chronic inflammation that consists primarily of eosinophils. Immunohistochemical staining reveals numerous cells that stain positive for S100 and CD1a. Which of the cells of the human immune system are responsible for this lesion?

A. Dendritic cells (Correct Answer)
B. T lymphocytes
C. Natural killer cells
D. B lymphocytes
E. Ciliary epithelium

Explanation: ***Dendritic cells*** - The description of the cells as having a "nodular pattern of abundant, granular, mildly eosinophilic cells with grooved nuclei with indented nuclear membranes" along with positive staining for **S100 and CD1a** is characteristic of **Langerhans cells**, which are a type of dendritic cell. - This constellation of findings is diagnostic of **Pulmonary Langerhans Cell Histiocytosis (PLCH)**, a rare interstitial lung disease almost exclusively seen in smokers, involving clonal proliferation of Langerhans cells. - The patient's heavy smoking history, cavitated upper and middle lobe nodules, and the specific immunohistochemical profile are pathognomonic for PLCH. *T lymphocytes* - While T lymphocytes are involved in immune responses and chronic inflammation, their morphology (smaller, round nuclei) and immunohistochemical markers (**CD3, CD4, CD8**) differ significantly from those described. - T lymphocytes are not typically identified by **S100 or CD1a** staining and do not form the characteristic cavitated nodules seen in PLCH. *Natural killer cells* - Natural killer (NK) cells are part of the innate immune system and are characterized by their cytotoxic activity against infected or cancerous cells. - Their morphology and typical markers (**CD16, CD56**) are distinct from the cells described in the biopsy, and they are not implicated in the pathogenesis of PLCH. *B lymphocytes* - B lymphocytes are crucial for humoral immunity, producing antibodies. They are characterized by specific markers such as **CD19, CD20, and surface immunoglobulins**. - The cellular morphology and immune markers of the lesion do not align with those of B lymphocytes. *Ciliary epithelium* - Ciliary epithelium lines the respiratory tract and functions in mucociliary clearance. It is a type of epithelial cell, **not an immune cell**. - These cells would not stain positive for **S100 or CD1a**, nor would they proliferate in a nodular, cavitating pattern as described in the lung lesion. - This option tests understanding that ciliary epithelium is not part of the immune system.

Question 24: A 28-year-old man is referred to the dermatologist for 2 months of increasing appearance of multiple smooth, circular patches of complete hair loss on his scalp. He says that the patches have associated pruritus and a burning sensation, and are not improving with the over-the-counter products recommended by his hair stylist. He denies pulling his hair intentionally. Physical examination reveals no epidermal inflammation or erythema, and no fluorescence is detected under Wood’s lamp. A punch biopsy shows a peribulbar lymphocytic inflammatory infiltrate surrounding anagen follicles, resembling a swarm of bees. Which of the following is the most likely diagnosis in this patient?

A. Telogen effluvium
B. Lichen planopilaris
C. Androgenic alopecia
D. Alopecia areata (Correct Answer)
E. Tinea capitis

Explanation: ***Alopecia areata*** - This diagnosis is strongly supported by the presence of **multiple smooth, circular patches of complete hair loss** and a biopsy showing a **peribulbar lymphocytic inflammatory infiltrate surrounding anagen follicles**, often described as a "swarm of bees" pattern. - The patient's young age and associated **pruritus and burning sensation** further align with the typical presentation of alopecia areata, an **autoimmune condition**. *Telogen effluvium* - This condition is characterized by **diffuse hair shedding**, often triggered by stress or systemic illness, and typically does not present as distinct, circular patches of complete hair loss. - A biopsy would show an increase in **telogen phase follicles**, not the peribulbar lymphocytic infiltrate seen here. *Lichen planopilaris* - This is a form of **scarring alopecia** where hair loss is typically accompanied by **perifollicular erythema, scaling, and inflammation**, which are absent in this patient. - Biopsy would reveal a **lichenoid interface dermatitis** with damage to the follicular epithelium, rather than a peribulbar lymphocytic infiltrate. *Androgenic alopecia* - Commonly known as **male-pattern baldness**, this condition presents with a characteristic pattern of hair thinning and loss from the temples and vertex, not smooth, circular patches. - The biopsy findings would show **follicular miniaturization**, without a significant inflammatory infiltrate. *Tinea capitis* - This is a **fungal infection** of the scalp, usually presenting with **scaly, erythematous patches with broken hairs** (black dots) and often inflammation or pustules. - Wood's lamp examination can sometimes show fluorescence, and a biopsy would reveal **fungal elements** within the hair shafts and follicles, which are not described here.

Question 25: A 15-year-old girl is brought to the physician by her mother for a 2-day history of abdominal pain, nausea, vomiting, diarrhea, and decreased appetite. Her last menstrual period was 3 weeks ago. Her temperature is 37.6°C (99.7°F). Abdominal examination shows tenderness to palpation with guarding in the right lower quadrant. Laboratory studies show a leukocyte count of 12,600/mm3. Which of the following is the most likely underlying cause of this patient's condition?

A. Fecalith impaction
B. Appendiceal lymphoid hyperplasia (Correct Answer)
C. Bacterial mesenteric lymphadenitis
D. Appendiceal luminal obstruction by foreign body
E. Viral gastroenteritis

Explanation: ***Appendiceal lymphoid hyperplasia*** - This is the **most common cause of appendicitis in children and adolescents** (ages 10-20), accounting for approximately **60-70% of pediatric cases**. - Lymphoid tissue in the appendix undergoes hyperplasia in response to **viral or bacterial infections**, leading to **luminal obstruction** and subsequent inflammation. - The patient's age (15 years), classic presentation of **right lower quadrant tenderness with guarding**, **leukocytosis**, and prodromal GI symptoms strongly support appendicitis due to this mechanism. - The **low-grade fever** and **diarrhea** suggest a preceding viral illness that triggered the lymphoid hyperplasia. *Fecalith impaction* - While fecaliths (calcified fecal matter) are a well-recognized cause of appendiceal obstruction, they account for only **30-40% of cases** and are **more common in adults** (>30 years). - In children and adolescents, **lymphoid hyperplasia** is the predominant cause, making this less likely given the patient's age. - The history of **diarrhea** also makes solid fecal impaction less probable. *Bacterial mesenteric lymphadenitis* - This is a **differential diagnosis** that can mimic appendicitis, **not a cause of appendicitis**. - Typically presents with more **diffuse abdominal pain** without the focal right lower quadrant peritoneal signs (guarding) seen in this patient. - Often caused by *Yersinia enterocolitica* or *Salmonella* species and associated with recent gastroenteritis. - The **focal RLQ guarding** in this patient makes true appendicitis more likely than mesenteric adenitis. *Appendiceal luminal obstruction by foreign body* - This is an **extremely rare** cause of appendicitis, reported primarily in case reports. - Would require a specific history of ingestion of indigestible items (seeds, pins, etc.), which is not present. - No clinical features suggest this etiology. *Viral gastroenteritis* - This is a **differential diagnosis**, **not a cause of appendicitis**. - While viral gastroenteritis can cause abdominal pain, nausea, vomiting, and diarrhea, it typically presents with **diffuse cramping** rather than focal tenderness. - The presence of **right lower quadrant guarding** (a peritoneal sign), **localized tenderness**, and **leukocytosis** strongly favor appendicitis over simple gastroenteritis. - Viral gastroenteritis rarely causes peritoneal signs or significant leukocytosis.

Question 26: A 34-year-old woman comes to the physician because of a 6-week history of fever and productive cough with blood-tinged sputum. She has also had a 4-kg (8.8-lb) weight loss during the same time period. Examination shows enlarged cervical lymph nodes. An x-ray of the chest shows a 2.5-cm pulmonary nodule in the right upper lobe. A biopsy specimen of the lung nodule shows caseating granulomas with surrounding multinucleated giant cells. Which of the following is the most likely underlying cause of this patient's pulmonary nodule?

A. Combined type III/IV hypersensitivity reaction
B. IgE-mediated mast cell activation
C. Immune complex deposition
D. Antibody-mediated cytotoxic reaction
E. Delayed T cell-mediated reaction (Correct Answer)

Explanation: ***Delayed T cell-mediated reaction*** - The presence of **caseating granulomas** with **multinucleated giant cells** is characteristic of tuberculosis, which is mediated by a **Type IV hypersensitivity reaction**. - This reaction involves **T cells** and **macrophages** forming granulomas to wall off persistent intracellular pathogens. *Combined type III/IV hypersensitivity reaction* - While granulomas can sometimes involve aspects of **Type III hypersensitivity** (immune complex deposition), **caseating granulomas** are primarily a feature of **Type IV (delayed T cell-mediated) hypersensitivity**. - **Type III reactions** are more typically associated with vasculitis or glomerulonephritis, which are not the primary features here. *IgE-mediated mast cell activation* - This describes a **Type I hypersensitivity reaction**, responsible for immediate allergic reactions like asthma or anaphylaxis. - The patient's symptoms (fever, weight loss, productive cough, granulomas) are not consistent with an **IgE-mediated response**. *Immune complex deposition* - This is characteristic of a **Type III hypersensitivity reaction**, where antigen-antibody complexes deposit in tissues, leading to inflammation and damage. - While Type III reactions can cause inflammation, they typically don't manifest as **caseating granulomas** and the chronic, progressive symptoms described. *Antibody-mediated cytotoxic reaction* - This describes a **Type II hypersensitivity reaction**, where antibodies directly bind to antigens on cell surfaces, leading to cell lysis (e.g., autoimmune hemolytic anemia). - The clinical picture of **granulomatous inflammation** is not consistent with a direct **antibody-mediated cytotoxic reaction**.

Question 27: A 36-year-old man is brought to the emergency department by his wife 20 minutes after having a seizure. Over the past 3 days, he has had a fever and worsening headaches. This morning, his wife noticed that he was irritable and demonstrated strange behavior; he put the back of his fork, the salt shaker, and the lid of the coffee can into his mouth. He has no history of serious illness and takes no medications. His temperature is 39°C (102.2°F), pulse is 88/min, and blood pressure is 118/76 mm Hg. Neurologic examination shows diffuse hyperreflexia and an extensor response to the plantar reflex on the right. A T2-weighted MRI of the brain shows edema and areas of hemorrhage in the left temporal lobe. Which of the following is most likely the primary mechanism of the development of edema in this patient?

A. Increased hydrostatic pressure
B. Breakdown of endothelial tight junctions (Correct Answer)
C. Release of vascular endothelial growth factor
D. Cellular retention of sodium
E. Degranulation of eosinophils

Explanation: ***Breakdown of endothelial tight junctions*** - The patient's symptoms (fever, headache, seizure, behavioral changes, focal neurological deficits) and MRI findings (edema, hemorrhage in the left temporal lobe) are highly suggestive of **herpes simplex encephalitis (HSE)**. - In HSE, the **inflammation** caused by viral infection leads to the breakdown of the **blood-brain barrier (BBB)**, primarily through the disruption of **endothelial tight junctions**, resulting in vasogenic edema and hemorrhage. *Increased hydrostatic pressure* - Increased hydrostatic pressure typically causes edema in conditions like **heart failure** or **venous obstruction**, where there is a systemic or localized increase in intravascular pressure. - While hydrostatic pressure contributes to fluid movement, it is not the primary mechanism of BBB breakdown and edema development in **viral encephalitis**, where inflammation-induced endothelial damage is key. *Release of vascular endothelial growth factor* - **VEGF** is a potent pro-angiogenic and permeability-enhancing factor often associated with **tumor-related edema** or certain inflammatory conditions where new vessel formation is prominent. - While it can increase vascular permeability, the primary and most direct mechanism for the widespread edema and hemorrhage described in acute viral encephalitis involves **direct endothelial damage and tight junction disruption**. *Cellular retention of sodium* - **Cellular retention of sodium** is characteristic of **cytotoxic edema**, which occurs when cellular energy failure (e.g., in ischemia) impairs the Na+/K+-ATPase pump, leading to intracellular water accumulation. - Although cytotoxic edema can coexist, the MRI findings of **hemorrhage** and significant interstitial edema point more strongly to **vasogenic edema** due to BBB disruption. *Degranulation of eosinophils* - **Eosinophil degranulation** is primarily associated with **allergic reactions**, **parasitic infections**, and certain **autoimmune vasculitides**. - While inflammation is present, eosinophils do not play a significant primary role in the mechanism of edema formation in acute viral encephalitis like HSE.

Question 28: A 3-year-old male is brought by his mother to the pediatrician because she is concerned about a lump in his neck. She reports that the child was recently ill with a cough, nasal congestion, and rhinorrhea. She also noticed that a small red lump developed on the patient’s neck while he was sick. Although his cough and congestion subsided after a few days, the neck lump has persisted. The child has no notable past medical history. He was born at 39 weeks gestation and is in the 55th percentiles for both height and weight. His temperature is 98.6°F (37°C), blood pressure is 105/65 mmHg, pulse is 90/min, and respirations are 18/min. Physical examination reveals a small, soft, rounded mass at the midline of the neck inferior to the hyoid bone. The mass is warm and tender to palpation. It moves superiorly when the patient drinks water. Histologic examination of this lesion would most likely reveal which of the following?

A. Stratified squamous epithelium associated with hair follicles and sebaceous glands
B. Randomly oriented papillae with fibrovascular cores and empty-appearing nuclei
C. Diffuse hyperplasia and hypertrophy of follicular cells
D. Follicular cells surrounding colloid and admixed with a neutrophilic infiltrate (Correct Answer)
E. Cyst-like structure lined by stratified squamous epithelium and containing mucoid material

Explanation: ***Follicular cells surrounding colloid and admixed with a neutrophilic infiltrate*** - The presentation of a **midline neck mass inferior to the hyoid bone** that moves with swallowing (drinking water), developing after an upper respiratory infection and being **warm and tender**, is highly suggestive of an infected **thyroglossal duct cyst**. - A thyroglossal duct cyst is derived from remnants of the **thyroglossal duct**, which is normally lined by **thyroid follicular epithelium**. In the presence of infection, such as a prior URI, these cysts can become inflamed, leading to the accumulation of **colloid**, **inflammatory cells (neutrophils)**, and debris within the cyst lumen. *Stratified squamous epithelium associated with hair follicles and sebaceous glands* - This describes the histological features of an **epidermoid cyst** or **pilar cyst**, which are typically found in the skin and contain keratinous material. - These cysts are usually **not midline** and do not typically move with swallowing, distinguishing them from the described lesion. *Randomly oriented papillae with fibrovascular cores and empty-appearing nuclei* - This histological description is characteristic of **papillary thyroid carcinoma**, specifically the **"orphan Annie eye" nuclei** often seen. - While thyroid tissue is involved, the overall clinical presentation (young child, symptomatic, recent infection, movable midline mass) is inconsistent with a malignant thyroid lesion. *Diffuse hyperplasia and hypertrophy of follicular cells* - This description is typical of **Graves' disease** or other causes of **diffuse goiter** due to **thyroid hyperactivity**. - The patient presents with a focal swelling rather than diffuse thyroid enlargement, and there are no signs of hyperthyroidism. *Cyst-like structure lined by stratified squamous epithelium and containing mucoid material* - This histology is characteristic of a **branchial cleft cyst**, which typically presents as a **lateral neck mass** (not midline). - Branchial cleft cysts are derived from remnants of the branchial arches and usually contain mucoid material, sometimes with squamous epithelium, but their location differs.

Question 29: A 50-year-old female presents to her physician with vesicles and tense blisters across her chest, arms, and the back of her shoulders. Physical examination reveals that blistering is not present in her oral mucosa, and the epidermis does not separate upon light stroking of the skin. The patient most likely suffers from a hypersensitivity reaction located:

A. Linearly along the epidermal basement membrane (Correct Answer)
B. In fat cells beneath the skin
C. In nuclei within epidermal cells
D. In net-like patterns around epidermal cells
E. In granular deposits at the tips of dermal papillae

Explanation: ***Linearly along the epidermal basement membrane*** - The description of **tense blisters** and the absence of **Nikolsky's sign** (no epidermal separation with light stroking) are characteristic features of **bullous pemphigoid**. - **Bullous pemphigoid** is an autoimmune disease where autoantibodies target components of the **hemidesmosomes** located along the **epidermal basement membrane**, leading to subepidermal blistering. *In fat cells beneath the skin* - This description is not consistent with any common blistering disorder, and **fat cells** (adipocytes) are not primary targets for blistering in autoimmune diseases. - Blistering disorders typically involve the epidermis or the dermal-epidermal junction, not the subcutaneous fat. *In nuclei within epidermal cells* - Autoantibodies targeting **nuclear antigens** are associated with conditions like **lupus erythematosus**, but this generally leads to characteristic skin rashes, not tense blistering. - Blistering from nuclear involvement is uncommon and does not match the clinical presentation of bullous pemphigoid or pemphigus. *In net-like patterns around epidermal cells* - This pattern of antibody deposition is characteristic of **pemphigus vulgaris**, where autoantibodies target **desmogleins** in the intercellular spaces of the epidermis. - Pemphigus vulgaris typically presents with **flaccid blisters** that are easily rupturable, and often involves the **oral mucosa**, in contrast to the patient's presentation. *In granular deposits at the tips of dermal papillae* - This pattern of IgA deposition, particularly in a granular fashion at the **dermal papillae tips**, is characteristic of **dermatitis herpetiformis**. - Dermatitis herpetiformis typically presents with **pruritic papules and vesicles**, often on extensor surfaces, and is commonly associated with **celiac disease**, which is not indicated here.

Question 30: A 6-year-old boy is brought to the emergency department due to a severe infection. Laboratory work shows leukocytosis of 60 × 109/L with marked left shift, but no blast cells. The patient is febrile and dehydrated. The physician believes that this is a severe reaction to the infection and orders a leukocyte alkaline phosphatase (LAP) stain on a peripheral smear. The LAP score is elevated. Which of the following statements best describes an additional characteristic of the condition this child is suffering from?

A. Chemotherapy is the treatment of choice.
B. Myeloblasts and promyelocytes are expected to be found.
C. This condition can lead to chronic myelocytic leukemia.
D. A blood count will contain band forms, metamyelocytes, and myelocytes. (Correct Answer)
E. The patient may develop anemia secondary to infection.

Explanation: ***A blood count will contain band forms, metamyelocytes, and myelocytes.*** - Leukocytosis with a **marked left shift** and **elevated LAP score** in the setting of severe infection is characteristic of a **leukemoid reaction**. - A leukemoid reaction involves the premature release of immature myeloid forms such as **band forms, metamyelocytes, and myelocytes** into the peripheral blood, mimicking leukemia. *Chemotherapy is the treatment of choice.* - **Chemotherapy** is typically used to treat malignancies like leukemia, not a **leukemoid reaction**, which is a reactive process to severe infection. - The primary treatment for a leukemoid reaction is to address the **underlying infection**. *Myeloblasts and promyelocytes are expected to be found.* - While there is a left shift, the question explicitly states "no blast cells," which differentiates a **leukemoid reaction** from acute leukemia. - **Myeloblasts** and **promyelocytes** are more characteristic of acute myeloid leukemia, where they constitute a significant percentage of cells. *This condition can lead to chronic myelocytic leukemia.* - A **leukemoid reaction** is a reactive process to infection and does not transform into **chronic myelocytic leukemia (CML)**. - CML is a myeloproliferative neoplasm characterized by the **BCR-ABL1 fusion gene** and a typically low LAP score, unlike the elevated LAP score seen here. *The patient may develop anemia secondary to infection.* - While **anemia of chronic disease** can occur with severe or prolonged infections, it is not the **additional characteristic** that best describes the leukemoid reaction itself, which primarily refers to the white blood cell changes. - The prominent feature described is the specific reactive pattern of **leukocytosis** and **left shift**.

Question 31: A 40-year-old man presents with a swollen left big toe that started this morning. The patient states that he attended a party last night and drank 4 glasses of whiskey. He denies any trauma to the foot. The patient has a history of similar episodes in the past that were related to alcohol use. His symptoms were previously relieved with ibuprofen. However, the pain persisted despite treatment with the medication. Physical examination reveals a tender and erythematous, swollen left 1st metatarsophalangeal joint. Which of the following events most likely contributed to his condition?

A. Upregulation of cellular adhesion molecules to promote neutrophil migration (Correct Answer)
B. Downregulation of integrins in the neutrophils
C. Vasoconstriction
D. Activation of cytosolic caspases
E. Decreased expression of selectin in the endothelium

Explanation: ***Upregulation of cellular adhesion molecules to promote neutrophil migration*** - This scenario describes an acute **gout attack**, characterized by severe inflammation in the **first metatarsophalangeal joint** (podagra) triggered by **alcohol intake**. - **Neutrophil migration** orchestrated by upregulated **cellular adhesion molecules** (e.g., selectins, integrins) is a central mechanism in acute gout, as neutrophils phagocytose **monosodium urate crystals**, leading to the release of inflammatory mediators. *Downregulation of integrins in the neutrophils* - **Downregulation of integrins** would impair neutrophil adhesion and migration into the inflamed joint, thereby **reducing** the inflammatory response, which contradicts the presented symptoms of severe inflammation. - Integrins are crucial for stable adhesion and **transmigration** of neutrophils through the endothelium. *Vasoconstriction* - **Vasoconstriction** would lead to reduced blood flow and typically present as **pallor** and **coldness** in the affected area, rather than the observed **erythema** and swelling characteristic of inflammation. - Acute inflammation, as seen in gout, is primarily associated with **vasodilation**, increasing blood flow to the site. *Activation of cytosolic caspases* - **Activation of cytosolic caspases** is a hallmark of **apoptosis** (programmed cell death), which is not the primary event driving the acute inflammatory response in gout. - While cell death can occur in inflammatory processes, the immediate cause of the excruciating pain and swelling in gout is the **inflammatory cascade** from crystal deposition. *Decreased expression of selectin in the endothelium* - **Decreased expression of selectin** on endothelial cells would hinder the initial "rolling" adhesion of neutrophils to the vessel wall, thereby **reducing** neutrophil recruitment and inflammatory exudation. - In acute inflammation, **selectin expression is upregulated** to facilitate the early stages of leukocyte extravasation.

Question 32: A 42-year-old woman with well-controlled HIV on antiretroviral therapy comes to the physician because of a 2-week history of a painless lesion on her right calf. Many years ago, she had a maculopapular rash over her trunk, palms, and soles that resolved spontaneously. Physical examination shows a 4-cm firm, non-tender, indurated ulcer with a moist, dark base and rolled edges. There is a similar lesion at the anus. Results of rapid plasma reagin testing are positive. Which of the following findings is most likely on microscopic examination of these lesions?

A. Epithelioid cell infiltrate surrounding acellular, granular core
B. Ulcerated epidermis with plasma cell infiltrate (Correct Answer)
C. Epidermal hyperplasia with dermal lymphocytic infiltrate
D. Lichenoid hyperplasia with superficial neutrophilic infiltrate
E. Coagulative necrosis surrounded by fibroblast and macrophage infiltrate

Explanation: ***Ulcerated epidermis with plasma cell infiltrate*** - The patient's history of a prior maculopapular rash involving palms and soles (secondary syphilis), current presentation of **painless, indurated ulcers with rolled edges** (gummas), and **positive RPR test** are diagnostic of **tertiary syphilis**. - **Gummas** are granulomatous lesions with coagulative necrosis, but the histologic **hallmark** that distinguishes syphilitic lesions from other granulomatous diseases is the **prominent plasma cell infiltrate** in the dermis beneath the **ulcerated epidermis**. - **Obliterative endarteritis** is also characteristic of syphilis at any stage. *Coagulative necrosis surrounded by fibroblast and macrophage infiltrate* - While gummas do contain **coagulative necrosis** surrounded by granulomatous inflammation, this description alone is **non-specific** and could describe many types of granulomas. - The distinguishing feature of syphilitic gummas is the **dense plasma cell infiltrate**, which is not captured in this option. - Without mentioning plasma cells, this description could apply to granulomas from tuberculosis, foreign body reactions, or other causes. *Epithelioid cell infiltrate surrounding acellular, granular core* - This describes a **tuberculoid (caseating) granuloma** characteristic of **tuberculosis** or **sarcoidosis**. - While syphilis can show granulomatous inflammation, the absence of plasma cells in this description makes it incorrect. - The "acellular, granular core" suggests caseous necrosis, which is more typical of TB than syphilis. *Lichenoid hyperplasia with superficial neutrophilic infiltrate* - **Lichenoid reactions** show a band-like lymphocytic infiltrate at the dermo-epidermal junction, seen in conditions like **lichen planus** or drug reactions. - **Neutrophilic infiltrates** suggest acute bacterial infections or neutrophilic dermatoses like **pyoderma gangrenosum**, not chronic spirochete infection. - This does not describe syphilitic histology. *Epidermal hyperplasia with dermal lymphocytic infiltrate* - This is a **non-specific** finding seen in various chronic inflammatory skin conditions like **chronic eczema** or **psoriasis**. - It lacks the specific features of syphilis, particularly the **prominent plasma cells** and granulomatous inflammation with necrosis. - This description is too generic to identify syphilitic gummas.

Question 33: A 37-year-old woman presents to the occupational health clinic for a new employee health screening. She has limited medical records prior to her immigration to the United States several years ago. She denies any current illness or significant medical history. Purified protein derivative (PPD) is injected on the inside of her left forearm for tuberculosis (TB) screening. Approximately 36 hours later, the patient comes back to the occupational health clinic and has an indurated lesion with bordering erythema measuring 15 mm in diameter at the site of PPD injection. Of the following options, which is the mechanism of her reaction?

A. Type III and IV–mixed immune complex and cell-mediated hypersensitivity reactions
B. Type III–immune complex-mediated hypersensitivity reaction
C. Type I–anaphylactic hypersensitivity reaction
D. Type II–cytotoxic hypersensitivity reaction
E. Type IV–cell-mediated (delayed) hypersensitivity reaction (Correct Answer)

Explanation: ***Type IV–cell-mediated (delayed) hypersensitivity reaction*** - The **PPD test** for tuberculosis is a classic example of a **Type IV hypersensitivity reaction**, also known as **delayed-type hypersensitivity (DTH)**. This reaction is orchestrated by **T lymphocytes** (specifically CD4+ T cells) that recognize antigens presented by antigen-presenting cells - The **induration** at 36 hours is a hallmark of this type of reaction, as it typically peaks between **24 to 72 hours** after antigen exposure, reflecting the time required for T cells to migrate to the site and initiate an inflammatory response. The immune response involves the release of **cytokines** leading to macrophage accumulation and localized tissue damage. *Type III and IV–mixed immune complex and cell-mediated hypersensitivity reactions* - While immune complexes (Type III) and cell-mediated reactions (Type IV) can both lead to tissue damage, a PPD test is primarily a **cell-mediated response** and is not characterized by significant immune complex deposition. - Mixed reactions are less common and usually involve a sustained presence of antigen leading to both types of responses, which is not the typical mechanism for an acute PPD skin test. *Type III–immune complex-mediated hypersensitivity reaction* - **Type III hypersensitivity** is characterized by the formation of **antigen-antibody immune complexes** that deposit in tissues, leading to inflammation and tissue damage, often seen in conditions like serum sickness or lupus nephritis. - The PPD reaction is based on T-cell recognition of mycobacterial antigens, not the deposition of soluble antigen-antibody complexes. *Type I–anaphylactic hypersensitivity reaction* - **Type I hypersensitivity** is an **immediate allergic reaction** mediated by **IgE antibodies** binding to mast cells and basophils, leading to histamine release upon re-exposure to an allergen. - This type of reaction typically occurs within minutes of exposure, not 36 hours later, and presents with symptoms like hives, angioedema, or anaphylaxis. *Type II–cytotoxic hypersensitivity reaction* - **Type II hypersensitivity** involves **antibodies (IgG or IgM)** binding to antigens on the surface of **host cells**, leading to cell lysis or dysfunction, often seen in transfusion reactions or autoimmune hemolytic anemia. - The PPD test does not involve direct antibody-mediated destruction of host cells.

Question 34: A 22-year-old woman comes to the physician because of pain and swelling of her left foot. Three days ago, she cut her foot on an exposed rock at the beach. Her temperature is 37.7°C (100°F). Examination of the left foot shows edema around a fluctuant erythematous lesion on the lateral foot. Which of the following is most likely the primary mechanism for the development of edema in this patient?

A. Decreased plasma oncotic pressure
B. Fluid production by bacteria
C. Increased capillary hydrostatic pressure
D. Separation of endothelial junctions (Correct Answer)
E. Systemic cytokine release

Explanation: ***Separation of endothelial junctions*** - The **cut to the foot** likely introduced bacteria, leading to a localized infection evident by the **erythematous, fluctuant lesion** and low-grade fever. - During **inflammation**, chemical mediators (like histamine and bradykinin) cause **endothelial cells to contract**, leading to the widening of inter-endothelial junctions, increasing **vascular permeability** and allowing fluid and proteins to leak into the interstitial space, causing edema. *Decreased plasma oncotic pressure* - This typically occurs in systemic conditions such as **liver failure** (decreased albumin production), **nephrotic syndrome** (protein loss in urine), or **severe malnutrition**. - There is no clinical evidence in the patient's presentation to suggest any of these systemic conditions are present. *Fluid production by bacteria* - While some bacteria can produce toxins or metabolic byproducts that contribute to inflammation, the **direct production of significant interstitial fluid** by bacteria themselves is not the primary mechanism of edema in bacterial infections. - Bacterial action primarily triggers the host's inflammatory response, which then leads to fluid accumulation. *Increased capillary hydrostatic pressure* - This typically results from **impaired venous return** (e.g., deep vein thrombosis, heart failure) or **arteriolar dilation**. - While local vasodilation occurs in inflammation, the primary mechanism of edema in localized infection is increased vascular permeability due to endothelial changes, not solely elevated hydrostatic pressure. *Systemic cytokine release* - While systemic cytokine release (e.g., in sepsis) can lead to **systemic capillary leak syndrome** and generalized edema, the patient's presentation describes a **localized infection** with localized edema. - The fever (37.7°C) is mild, suggesting a localized rather than severe systemic inflammatory response at this stage.

Question 35: A 23-year-old woman comes to the physician because of right-sided blurry vision and eye pain for 4 days. She has a 6-day history of low-grade fever, headache, and malaise. One year ago, she was diagnosed with Crohn disease. Her only medication is prednisone. Her temperature is 38°C (100.4°F), pulse is 84/min, and blood pressure is 112/75 mm Hg. The right eyelid is erythematous and tender; there are multiple vesicles over the right forehead and the tip of the nose. Visual acuity is 20/20 in the left eye and 20/80 in the right eye. Extraocular movements are normal. The right eye shows conjunctival injection and reduced corneal sensitivity. Fluorescein staining shows a corneal lesion with a tree-like pattern. Which of the following is the most likely diagnosis?

A. Angle-closure glaucoma
B. Herpes zoster keratitis (Correct Answer)
C. Anterior uveitis
D. Herpes simplex keratitis
E. Pseudomonas keratitis

Explanation: ***Herpes zoster keratitis*** - The presence of **vesicles on the forehead and tip of the nose** (Hutchinson sign) indicates involvement of the nasociliary nerve, pathognomonic for ophthalmic herpes zoster. - **Tree-like pattern** on fluorescein staining, along with reduced corneal sensitivity and unilateral blurry vision, are characteristic features of herpes zoster keratitis. *Angle-closure glaucoma* - Typically presents with **sudden, severe eye pain**, blurred vision, headache, and sometimes nausea/vomiting, usually without a preceding viral prodrome or skin lesions. - While it can cause blurry vision, it would not explain the **vesicular rash** or **tree-like corneal ulcer** observed in this patient. *Anterior uveitis* - Often associated with Crohn disease and features eye pain, photophobia, and blurred vision, but typically **lacks the characteristic vesicular rash** on the skin. - Fluorescein staining would not show a **tree-like lesion**; inflammation of the iris and ciliary body is seen. *Herpes simplex keratitis* - Can cause dendritic or tree-like corneal lesions and reduced corneal sensitivity, but typically **does not present with a rash on the forehead and tip of the nose** (Hutchinson sign). - Herpes simplex usually affects the eye directly without dermatomal involvement. *Pseudomonas keratitis* - A highly aggressive bacterial infection, often associated with **contact lens use**, presents with rapid onset of severe pain, purulent discharge, and a dense corneal infiltrate, usually an ulcer. - It would not cause a **vesicular rash** on the forehead or a tree-like pattern on fluorescein staining, which points to a viral etiology.

Question 36: A 4-year-old Caucasian boy is brought by his mother to the pediatrician with a red and swollen elbow. He was playing outside a few days prior to presentation when he fell and lightly scraped his elbow on the sidewalk. He was born at 34 weeks' gestation and was in the neonatal ICU for 2 days. His temperature is 102.1°F (38.9°C), blood pressure is 105/65 mmHg, pulse is 110/min, and respirations are 20/min. On exam, he has a swollen, erythematous, fluctuant, and exquisitely tender mass on his right elbow. There is expressible purulence coming from his wound. A peripheral blood smear in this patient would most likely reveal which of the following findings?

A. Absence of dark blue cytoplasmic staining upon nitroblue tetrazolium administration
B. Neutrophils with peroxidase-negative granules
C. Neutrophils with pale cytoplasm without granules
D. Neutrophils with abundant peroxidase-positive granules (Correct Answer)
E. Macrocytic erythrocytes and acanthocytes

Explanation: ***Neutrophils with abundant peroxidase-positive granules*** - This patient presents with a **typical acute bacterial skin and soft tissue infection** (abscess) following minor trauma. This is a **normal, age-appropriate scenario** in a healthy child. - In response to acute bacterial infection, the peripheral blood smear would show **normal, mature neutrophils with abundant peroxidase-positive (myeloperoxidase-positive) granules**. This is the **standard appearance of healthy, functioning neutrophils** responding to infection. - Additional findings might include **leukocytosis** with a **left shift** (increased band forms), but the neutrophils themselves would have normal morphology with prominent azurophilic (primary) and specific (secondary) granules that stain positive for peroxidase. - This is the expected finding in any patient with an acute bacterial infection and a normal immune system. *Absence of dark blue cytoplasmic staining upon nitroblue tetrazolium administration* - The **nitroblue tetrazolium (NBT) test** is a specialized diagnostic test for **Chronic Granulomatous Disease (CGD)**, where neutrophils cannot produce a respiratory burst due to defective NADPH oxidase. - However, this patient shows **no clinical evidence of CGD**: this is a **first-time infection** (not recurrent), occurring after **significant environmental exposure** (playing outside, scraping elbow on sidewalk), and the infection is responding as expected to inflammation. - Additionally, NBT testing is a **functional assay**, not a routine finding on peripheral blood smear examination. *Neutrophils with peroxidase-negative granules* - **Myeloperoxidase deficiency** is a rare neutrophil disorder where granules lack myeloperoxidase enzyme. - There is **no clinical indication** for this diagnosis in a child with a straightforward post-traumatic bacterial infection. - Most patients with myeloperoxidase deficiency are **asymptomatic** or have only mild infection susceptibility. *Neutrophils with pale cytoplasm without granules* - **Hypogranular or agranular neutrophils** are seen in **Chediak-Higashi syndrome** (which includes oculocutaneous albinism and neurologic abnormalities) or **myelodysplastic syndromes**. - This patient has an **acute infection with normal inflammatory response**, making these conditions extremely unlikely. - Chediak-Higashi syndrome would present with additional features like partial albinism and easy bruising. *Macrocytic erythrocytes and acanthocytes* - **Macrocytic erythrocytes** suggest vitamin B12/folate deficiency, liver disease, or hypothyroidism. - **Acanthocytes** (spur cells) are associated with severe liver disease, abetalipoproteinemia, or neuroacanthocytosis. - These red blood cell abnormalities are **completely unrelated** to this patient's presentation of acute bacterial skin infection.

Question 37: Two days after being admitted for acute myocardial infarction, a 61-year-old man has sharp, substernal chest pain that worsens with inspiration and improves when leaning forward. Cardiac examination shows a scratchy sound best heard over the left sternal border. Histopathological examination of the infarcted myocardial tissue is most likely to show which of the following findings?

A. Neutrophilic infiltration
B. Collagenous scar tissue
C. Normal myocardium
D. Coagulative necrosis (Correct Answer)
E. Granulation tissue with macrophages

Explanation: ***Coagulative necrosis*** - The patient's clinical presentation (sharp, substernal chest pain, worsening with inspiration, improving while leaning forward, and a scratchy pericardial friction rub) indicates **post-MI fibrinous pericarditis**, a common complication occurring 2-4 days after myocardial infarction. - At **day 2 post-MI**, the infarcted myocardium demonstrates **coagulative necrosis** as the primary and most characteristic histopathological finding, representing irreversible ischemic cell death with preserved tissue architecture. - While neutrophilic infiltration is also present at this timepoint, coagulative necrosis of the cardiomyocytes themselves is the defining pathological feature that distinguishes irreversible myocardial injury. *Neutrophilic infiltration* - **Neutrophilic infiltration** is indeed present at day 2 post-MI (peaks at days 1-3) as part of the acute inflammatory response to clear necrotic debris. - However, neutrophils represent the **reactive inflammatory response** rather than the primary pathological change in the infarcted cardiomyocytes themselves. - The question asks about the most characteristic histopathological finding, which is the **coagulative necrosis** of the myocardial cells, not the secondary inflammatory infiltrate. *Collagenous scar tissue* - **Collagenous scar tissue** forms much later during the remodeling phase, typically **7 weeks or more** after MI, representing the final stage of healing. - At day 2, the tissue is still in the acute phase of coagulative necrosis and early inflammation, far too early for mature fibrous scar formation. *Normal myocardium* - The patient has sustained an **acute myocardial infarction** with irreversible injury to cardiac tissue. - Histopathological examination of the infarcted region would show clear abnormalities, not **normal myocardium**. *Granulation tissue with macrophages* - **Granulation tissue** with fibroblasts, new capillaries, and macrophages begins forming during the proliferative phase, typically starting around **days 5-7** post-MI. - At day 2, it is too early for granulation tissue formation; the tissue is still dominated by coagulative necrosis and acute neutrophilic inflammation.

Question 38: A 42-year-old man comes to the physician because of a 6-week history of intermittent fever, abdominal pain, bloody diarrhea, and sensation of incomplete rectal emptying. He also has had a 4.5-kg (10-lb) weight loss over the past 3 months. Abdominal examination shows diffuse tenderness. Colonoscopy shows circumferential erythematous lesions that extend without interruption from the anal verge to the cecum. A biopsy specimen taken from the rectum shows mucosal and submucosal inflammation with crypt abscesses. This patient is most likely at risk of developing colon cancer with which of the following characteristics?

A. Low-grade lesion
B. Unifocal lesion
C. Non-polypoid dysplasia (Correct Answer)
D. Late p53 mutation
E. Early APC mutation

Explanation: ***Non-polypoid dysplasia*** - The patient's symptoms (bloody diarrhea, abdominal pain, crypt abscesses, continuous inflammation extending to the cecum) are highly suggestive of **ulcerative colitis (UC)**. - In UC, the chronic inflammation causes a field defect across the colonic mucosa, leading to a higher risk of **non-polypoid (flat) dysplasia** and subsequent colon cancer (colitis-associated cancer). *Low-grade lesion* - While dysplasia can be low-grade, the primary characteristic of colon cancer development in UC is the **type of growth** (flat/non-polypoid) rather than simply its grade. - The presence and progression of **dysplasia** (regardless of initial grade) are critical for risk stratification in UC. *Unifocal lesion* - Colitis-associated cancer in UC often arises from widespread field changes due to chronic inflammation, making **multifocal or diffuse dysplasia** more common than a single, isolated lesion. - The diffuse nature of UC inflammation across the colon makes a unifocal cancerous change less typical compared to sporadic colon cancer. *Late p53 mutation* - **p53 mutations** are commonly found in colitis-associated colon cancer and are generally considered an **early event** in the progression from dysplasia to invasive carcinoma, rather than a late one. - Mutations in tumor suppressor genes like **p53** contribute to genomic instability early in the neoplastic process. *Early APC mutation* - **APC mutations** are a hallmark of **sporadic colorectal cancer** and familial adenomatous polyposis (FAP), where they typically initiate the adenoma-carcinoma sequence. - In **colitis-associated cancer**, APC mutations are less frequently the initiating event and often occur later, with other pathways (e.g., p53, microsatellite instability) being more prominent in early carcinogenesis.

Question 39: A 12-month-old boy is brought to the physician by his parents for a 4-week history of fever, malaise, cough, and difficulty breathing. He has had recurrent episodes of gastroenteritis since birth. Cardiopulmonary examination shows subcostal retractions and crackles bilaterally. There is enlargement of the cervical, axillary, and inguinal lymph nodes. An x-ray of the chest shows bilateral consolidations. A sputum culture shows colonies of Burkholderia cepacia. A blood sample is obtained and after the addition of nitroblue tetrazolium to the sample, neutrophils remain colorless. A defect in which of the following is the most likely cause of this patient's condition?

A. Microtubule polymerization
B. NADPH oxidase complex (Correct Answer)
C. Actin filament assembly
D. T cell CD40 ligand
E. B cell maturation

Explanation: ***NADPH oxidase complex*** - The presentation with recurrent infections, particularly with **Burkholderia cepacia**, and the **colorless nitroblue tetrazolium (NBT) test result** are classic findings for **chronic granulomatous disease (CGD)**. - CGD is caused by a defect in the **NADPH oxidase complex** within phagocytes, impairing their ability to generate reactive oxygen species (*respiratory burst*) necessary to kill certain bacteria and fungi. *Microtubule polymerization* - A defect in microtubule polymerization is associated with conditions like **Chédiak-Higashi syndrome**, which involves impaired lysosome function and neutropenia, leading to recurrent infections. - However, Chédiak-Higashi syndrome typically presents with **partial oculocutaneous albinism**, peripheral neuropathy, and Giant granules on blood smears, none of which are described here. *Actin filament assembly* - Defects in actin filament assembly can cause conditions like **Wiskott-Aldrich syndrome**, characterized by immunodeficiency, thrombocytopenia, and eczema. - This patient's presentation with specific infection types and a positive NBT test points away from a primary actin defect. *T cell CD40 ligand* - A defect in the **T cell CD40 ligand** causes **X-linked hyper-IgM syndrome**, characterized by recurrent bacterial infections and very low levels of IgG, IgA, and IgE, with normal or elevated IgM. - While this is an immunodeficiency, the specific infection with *Burkholderia cepacia* and the NBT test result are not characteristic of hyper-IgM syndrome. *B cell maturation* - Defects in B cell maturation, such as **X-linked agammaglobulinemia (XLA)**, lead to a lack of mature B cells and significantly reduced levels of all immunoglobulin classes. - Patients with XLA typically suffer from recurrent bacterial infections, but *Burkholderia cepacia* and the NBT test result are not specific to this condition.

Question 40: A 33-year-old woman comes to the physician because of a 4-day history of fever, anterior neck pain, and throat swelling. She has no history of serious illness. Her temperature is 38.1°C (100.6°F) and pulse is 109/min. Physical examination shows diaphoresis and a fine tremor of the outstretched hands. The thyroid gland is enlarged, firm, and tender to palpation. Serum thyroid stimulating hormone level is 0.06 μU/mL and erythrocyte sedimentation rate is 65 mm/h. 123I scan shows an enlarged thyroid gland with diffusely decreased uptake. Histologic examination of a thyroid biopsy specimen is most likely to show which of the following findings?

A. Undifferentiated giant cells with areas of necrosis and hemorrhage
B. Noncaseating granulomas with multinucleated giant cells (Correct Answer)
C. Lymphocytic infiltration with germinal follicle formation
D. Follicular epithelial cell hyperplasia
E. Concentric intracellular lamellar calcifications

Explanation: ***Noncaseating granulomas with multinucleated giant cells*** - This finding is characteristic of **subacute granulomatous (de Quervain) thyroiditis**, which is supported by the patient's symptoms: anterior neck pain, fever, elevated ESR, and tender thyroid. - The **low TSH and decreased radioactive iodine uptake** indicate thyroid damage with release of preformed thyroid hormones, typical of the initial thyrotoxic phase of this condition. *Undifferentiated giant cells with areas of necrosis and hemorrhage* - This description is more consistent with **anaplastic thyroid carcinoma**, a highly aggressive malignancy, which is unlikely in a 33-year-old woman presenting with a 4-day history of symptoms. - Anaplastic carcinoma would typically cause a rapidly enlarging, fixed, and firm mass, often with obstructive symptoms, rather than a tender gland with signs of thyrotoxicosis. *Lymphocytic infiltration with germinal follicle formation* - This is the histological hallmark of **Hashimoto's thyroiditis**, an autoimmune condition leading to hypothyroidism. - Patients with Hashimoto's typically present with hypothyroidism, goiter, and positive thyroid antibodies, not acute pain, fever, or the transient thyrotoxicosis seen here. *Follicular epithelial cell hyperplasia* - This is seen in conditions causing chronic stimulation of the thyroid gland, such as **diffuse toxic goiter (Graves' disease)** or in patients with iodine deficiency. - Graves' disease would present with hyperthyroidism and diffuse uptake on a radioactive iodine scan, which contradicts the "diffusely decreased uptake" seen in this patient. *Concentric intracellular lamellar calcifications* - These are known as **Psammoma bodies** and are characteristic of **papillary thyroid carcinoma**. - Papillary thyroid carcinoma is typically a slow-growing, painless mass and is not associated with acute inflammatory symptoms like fever, pain, and a very elevated ESR.

Question 41: A 61-year-old-male underwent deceased donor liver transplantation 3 weeks ago. During his follow up visit he complains of nausea and abdominal pain. He has been taking all of his medications as prescribed. He has a history of alcohol abuse and his last drink was one year ago. He does not smoke cigarettes and lives at home with his wife. On physical examination temperature is 98.6°F (37°C), blood pressure is 115/80 mmHg, pulse is 90/min, respirations are 18/min, and pulse oximetry is 99% on room air. He has scleral icterus and a positive fluid wave. Liver function tests are as follows: Alkaline phosphatase: 110 U/L Aspartate aminotransferase (AST, GOT): 100 U/L Alanine aminotransferase (ALT, GPT): 120 U/L Bilirubin total: 2.2 mg/dL Liver biopsy shows mixed dense interstitial lymphocytic infiltrates in the portal triad. What is the mechanism of this reaction?

A. Grafted T lymphocytes reacting against host
B. CD4+ T lymphocytes reacting against recipient APCs
C. CD8+ T lymphocytes reacting against donor MHCs (Correct Answer)
D. Acute viral infection
E. Pre-existing recipient antibodies

Explanation: ***CD8+ T lymphocytes reacting against donor MHCs*** - This scenario describes **acute cellular rejection** following liver transplantation, mediated primarily by **recipient CD8+ T lymphocytes** recognizing donor major histocompatibility complex (MHC) class I molecules on donor hepatocytes. - The **lymphocytic infiltrates** in the portal triad are characteristic of acute rejection, where activated cytotoxic T cells attack the transplanted organ. *Grafted T lymphocytes reacting against host* - This mechanism describes **graft-versus-host disease (GVHD)**, which is much more common after hematopoietic stem cell transplantation. - While liver allografts contain donor lymphocytes, **GVHD from liver transplant is rare** and typically only seen in highly immunosuppressed patients or specific transplant settings. *CD4+ T lymphocytes reacting against recipient APCs* - This describes a reaction of donor CD4+ T cells against recipient antigen-presenting cells (APCs), which is part of the mechanism for **graft-versus-host disease (GVHD)**. - The primary pathology in this patient, with liver damage and lymphocytic infiltration of the portal triad, points to a rejection of the transplanted liver, not GVHD. *Acute viral infection* - While possible in transplant recipients, an acute viral infection would typically present with different patterns of liver injury and biopsy findings, such as **viral cytopathic effects** or more widespread inflammation distinct from the dense portal triad infiltrates typical of rejection. - The clinical presentation and biopsy findings are classic for organ rejection rather than a viral infection. *Pre-existing recipient antibodies* - **Pre-existing recipient antibodies** are primarily responsible for **hyperacute rejection**, which occurs minutes to hours after transplant and leads to rapid graft failure. - This patient is presenting 3 weeks post-transplant, which is too late for hyperacute rejection; this mechanism generally leads to thrombosis and necrosis, not the interstitial lymphocytic infiltrates seen here.

Question 42: A 23-year-old woman comes to the physician because of a 5-month history of a pruritic rash on the bilateral upper extremities. She has no history of serious illness and takes no medications. A skin biopsy of the rash shows intraepidermal accumulation of edematous fluid and widening of intercellular spaces between keratinocytes. Which of the following is the most likely diagnosis?

A. Dermatitis herpetiformis
B. Eczematous dermatitis (Correct Answer)
C. Acanthosis nigricans
D. Lichen planus
E. Psoriasis vulgaris

Explanation: ***Eczematous dermatitis*** - The biopsy findings of **intraepidermal edema** and **widening of intercellular spaces between keratinocytes (spongiosis)** are classic histopathologic features of eczematous dermatitis. - The clinical presentation of a **pruritic rash** on the upper extremities further supports this diagnosis, as eczema is characterized by itching and inflammation. *Dermatitis herpetiformis* - This condition is characterized by **subepidermal vesicles** and **neutrophilic infiltrates** in the dermal papillae, with IgA deposition, which differs from the findings described. - It is strongly associated with **celiac disease** and presents with intensely pruritic, grouped papules and vesicles, predominantly on extensor surfaces. *Acanthosis nigricans* - Histologically, acanthosis nigricans shows **papillomatosis** and **hyperkeratosis**, with epidermal thickening, rather than intraepidermal edema or spongiosis. - Clinically, it presents as **hyperpigmented, velvety plaques** in intertriginous areas, not a generalized pruritic rash. *Lichen planus* - Biopsy of lichen planus would reveal a **band-like lymphocytic infiltrate** at the dermoepidermal junction, **sawtooth rete ridges**, and **Civatte bodies**. - Clinically, it often presents with **pruritic, polygonal, purple, planar papules and plaques** (the 6 Ps), which is not consistent with the described rash. *Psoriasis vulgaris* - Histopathologically, psoriasis is characterized by **acanthosis**, **parakeratosis**, **Munro microabscesses**, and **dilated blood vessels** in the dermal papillae. - Clinically, it manifests as **erythematous plaques with silvery scales**, typically on extensor surfaces, distinguishing it from a generalized pruritic rash with spongiosis.

Question 43: A 27-year-old woman presents to the emergency department for fever and generalized malaise. Her symptoms began approximately 3 days ago, when she noticed pain with urination and mild blood in her urine. Earlier this morning she experienced chills, flank pain, and mild nausea. Approximately 1 month ago she had the "flu" that was rhinovirus positive and was treated with supportive management. She has a past medical history of asthma. She is currently sexually active and uses contraception inconsistently. She occasionally drinks alcohol and denies illicit drug use. Family history is significant for her mother having systemic lupus erythematosus. Her temperature is 101°F (38.3°C), blood pressure is 125/87 mmHg, pulse is 101/min, and respirations are 18/min. On physical examination, she appears uncomfortable. There is left-sided flank, suprapubic, and costovertebral angle tenderness. Urine studies are obtained and a urinalysis is demonstrated below: Color: Amber pH: 6.8 Leukocyte: Positive Protein: Trace Glucose: Negative Ketones: Negative Blood: Positive Nitrite: Positive Leukocyte esterase: Positive Specific gravity: 1.015 If a renal biopsy is performed in this patient, which of the following would most likely be found on pathology?

A. Diffuse capillary and glomerular basement membrane thickening
B. Suppurative inflammation with interstitial neutrophilic infiltration (Correct Answer)
C. Mesangial proliferation
D. Focal and segmental sclerosis of the glomeruli and mesangium
E. Granulomatous inflammation with epithelioid macrophages

Explanation: ***Suppurative inflammation with interstitial neutrophilic infiltration*** - The patient's symptoms (fever, chills, flank pain, dysuria, hematuria) and positive urinalysis (nitrite, leukocyte esterase, WBCs) are highly indicative of **acute pyelonephritis**, a bacterial infection of the kidney. - A renal biopsy in acute pyelonephritis typically shows **suppurative (purulent) inflammation** characterized by an influx of **neutrophils** into the renal interstitium and tubules, representing acute inflammation. - This is the hallmark pathological finding in acute bacterial pyelonephritis. *Diffuse capillary and glomerular basement membrane thickening* - This finding is characteristic of **membranous nephropathy**, a cause of nephrotic syndrome presenting with proteinuria and edema, not an acute infection. - The patient's clinical presentation with fever, flank pain, and signs of bacterial infection does not align with membranous nephropathy. *Granulomatous inflammation with epithelioid macrophages* - **Granulomatous inflammation** is a chronic inflammatory pattern seen in conditions like **tuberculosis, sarcoidosis, or fungal infections**. - The acute presentation, positive nitrites (indicating gram-negative bacteria), and clinical course are inconsistent with granulomatous disease, which would have a more indolent course. *Mesangial proliferation* - **Mesangial proliferation** is a feature of glomerular diseases like **IgA nephropathy** (which can present after upper respiratory infection) or lupus nephritis. - While the patient has a family history of lupus, her acute infectious symptoms with positive nitrites indicate bacterial pyelonephritis, not a glomerular disease. *Focal and segmental sclerosis of the glomeruli and mesangium* - This finding is characteristic of **Focal Segmental Glomerulosclerosis (FSGS)**, a primary glomerular disease that typically presents with nephrotic syndrome (heavy proteinuria, edema, hypoalbuminemia). - The patient's acute infectious symptoms and signs of urinary tract infection are inconsistent with FSGS.

Question 44: A 45-year-old immigrant presents with unintentional weight loss, sleep hyperhidrosis, and a persistent cough. He says these symptoms have been present for quite some time. Upon imaging, many granulomas in the upper lobes are present. It is noted that these apical granulomas have centers of necrosis that appear cheese-like in appearance. Encircling the area of necrosis are large cells with cytoplasms pale in color. Of the following surface markers, which one is most closely associated with these cells?

A. CD20
B. CD3
C. CD4
D. CD14 (Correct Answer)
E. CD8

Explanation: ***CD14*** - The description of **caseating granulomas** in the upper lobes with large cells having pale cytoplasm points towards **tuberculosis** and the presence of **epithelioid macrophages**. - **CD14** is a surface marker commonly found on **monocytes** and **macrophages**, making it the most appropriate choice among the given options. - Note: While epithelioid macrophages (the activated form seen in granulomas) may downregulate CD14 compared to circulating monocytes, CD14 remains the most closely associated macrophage marker among these choices. **CD68** would be the ideal marker for tissue macrophages, but it is not listed. *CD20* - **CD20** is a surface marker characteristic of **B lymphocytes**. - While B cells might be present in inflammatory lesions, they are not the predominant cell type described as "large cells with pale cytoplasm" forming the granuloma. *CD3* - **CD3** is a pan T-cell marker, indicating the presence of all types of **T lymphocytes**. - While T cells (specifically CD4+ T helper cells) are crucial in granuloma formation, the "large cells with pale cytoplasm" encasing the necrosis specifically refer to epithelioid macrophages, not T cells. *CD4* - **CD4** is a surface marker for **helper T lymphocytes**. - **CD4+ T cells** play a critical role in orchestrating the immune response and granuloma formation in tuberculosis through IFN-γ secretion, but the description of the large cells with pale cytoplasm refers to macrophages, not lymphocytes. *CD8* - **CD8** is a surface marker for **cytotoxic T lymphocytes**. - **CD8+ T cells** are also involved in the immune response to mycobacterial infection but are not the primary cell type described as forming the bulk of the granuloma's characteristic "large cells with pale cytoplasm."

Question 45: A 39-year-old male presents to your office with nodular skin lesions that progress from his right hand to right shoulder. The patient reports that the initial lesion, currently necrotic and ulcerative, developed from an injury he received while weeding his shrubs a couple weeks earlier. The patient denies symptoms of respiratory or meningeal disease. Which of the following most likely characterizes the pattern of this patient’s skin lesions:

A. Contact dermatitis
B. Dermatophyte colonization
C. Hematogenous dissemination
D. Arthropod bite
E. Ascending lymphangitis (Correct Answer)

Explanation: ***Ascending lymphangitis*** - The patient's presentation of a primary lesion on the hand that progresses to nodular lesions along the right arm to the shoulder, following an injury sustained while gardening, is characteristic of **sporotrichosis**. - **Sporotrichosis** causes **lymphocutaneous spread** via the lymphatic system, manifesting as a chain of nodules along lymphatic channels, which is consistent with ascending lymphangitis. *Contact dermatitis* - This condition involves an **inflammatory reaction** of the skin to an irritant or allergen, typically presenting as an itchy rash, redness, and sometimes blisters, - It does not usually result in distinct nodular lesions that specifically track along lymphatic pathways in an ascending pattern. *Dermatophyte colonization* - This refers to a superficial fungal infection affecting the skin, hair, or nails, causing conditions like **tinea corporis** or **tinea pedis**. - Dermatophyte infections typically present as **ring-shaped lesions** with central clearing or scaling and do not cause ascending nodular lesions along lymphatic routes. *Hematogenous dissemination* - This route involves the spread of pathogens through the **bloodstream**, leading to systemic infection or multiple lesions in various, often distant, organs or skin sites. - While it can manifest with skin lesions, the specific pattern of **localized trauma followed by ascending nodules** along a limb is more indicative of lymphatic spread rather than systemic hematogenous dissemination. *Arthropod bite* - An arthropod bite typically results in a **localized reaction** at the site of the bite, such as a wheal, papule, or erythema, often accompanied by itching or pain. - While an arthropod bite could be an initial injury, it would not directly explain the subsequent development of multiple, progressively ascending nodular lesions characteristic of lymphatic spread.

Question 46: A 36-year-old man is admitted to the hospital because of a 1-day history of epigastric pain and vomiting. He has had similar episodes of epigastric pain in the past. He drinks 8 oz of vodka daily. Five days after admission, the patient develops aspiration pneumonia and sepsis. Despite appropriate therapy, the patient dies. At autopsy, the pancreas appears gray, enlarged, and nodular. Microscopic examination of the pancreas shows localized deposits of calcium. This finding is most similar to an adaptive change that can occur in which of the following conditions?

A. Primary hyperparathyroidism
B. Sarcoidosis
C. Multiple myeloma
D. Congenital CMV infection
E. Chronic kidney disease (Correct Answer)

Explanation: ***Chronic kidney disease*** - The pancreatic finding represents **dystrophic calcification** (calcium deposition in damaged tissue with normal serum calcium levels), a consequence of chronic pancreatitis. - **Chronic kidney disease** is the most similar condition because it also involves pathologic calcification as an adaptive/pathologic change, though through a different mechanism called **metastatic calcification**. - In CKD, **hyperphosphatemia** and secondary **hyperparathyroidism** elevate the serum calcium-phosphate product, leading to calcium deposition in **normal tissues** (blood vessels, kidneys, lungs, gastric mucosa). - Both conditions demonstrate **pathologic calcification as a tissue response** to metabolic derangement, making CKD the best answer among the options provided. *Primary hyperparathyroidism* - Causes **hypercalcemia** and **hypophosphatemia** due to excess PTH secretion. - Can lead to **metastatic calcification** in normal tissues, but is less commonly associated with widespread tissue calcification compared to CKD. - The mineral imbalance pattern differs from CKD (high calcium, low phosphate vs. high phosphate, variable calcium). *Sarcoidosis* - Causes **hypercalcemia** due to increased 1,25-dihydroxyvitamin D production by activated macrophages in granulomas. - Can result in **metastatic calcification**, particularly nephrocalcinosis. - However, this is less common and less extensive than the calcification seen in CKD. *Multiple myeloma* - Produces **hypercalcemia** through osteolytic bone destruction and cytokine-mediated bone resorption. - Can theoretically cause **metastatic calcification**, but this is not a typical or prominent feature of the disease. - The hypercalcemia is usually addressed before significant tissue calcification occurs. *Congenital CMV infection* - Causes **dystrophic calcification** in damaged tissues, typically **periventricular intracranial calcifications**. - While this involves the same type of calcification (dystrophic), CMV infection is not characterized by systemic or progressive calcification as an adaptive metabolic response. - The calcifications are focal sequelae of viral tissue damage, not a widespread metabolic derangement.

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