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?
Q22
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?
Q23
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?
Q24
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?
Q25
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?
Q26
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?
Q27
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?
Q28
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?
Q29
A 19-year-old man presents with painful oral ulcers and rash. He says that his symptoms started 1 week ago with a low-grade fever, malaise, and cough. Then, 3 days ago, he noted small painful red bumps on his hands and feet, which quickly worsened and spread to involve his extremities and upper torso. At the same time, multiple painful oral ulcers appeared, which have not improved. He denies any trouble breathing, pruritus, hemoptysis, hematochezia, or similar symptoms in the past. Past medical history is significant for a recent methicillin-resistant staphylococcus aureus (MRSA) skin infection 2 weeks ago secondary to a laceration on his left leg for which he has been taking trimethoprim-sulfamethoxazole. No other current medications. The patient is afebrile, and his vital signs are within normal limits. Physical examination reveals multiple raised, erythematous, circular papules averaging 1–2 cm in diameter with a central bulla, as shown in the exhibit (see image below). The cutaneous lesions occupy < 10% of his total body surface area (BSA). Nikolsky sign is negative. Multiple mucosal erosions are noted in the oral cavity. Generalized lymphadenopathy is present. A well-healing laceration is present on the left leg with no evidence of drainage or fluctuance. A cutaneous punch biopsy of one of the lesions is performed. Which of the following histopathologic features would most likely be found on this patient's biopsy?
Q30
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?
Inflammation US Medical PG Practice Questions and MCQs
Question 21: 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 22: 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 23: 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 24: 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 25: 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 26: 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 27: 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 28: 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 29: A 19-year-old man presents with painful oral ulcers and rash. He says that his symptoms started 1 week ago with a low-grade fever, malaise, and cough. Then, 3 days ago, he noted small painful red bumps on his hands and feet, which quickly worsened and spread to involve his extremities and upper torso. At the same time, multiple painful oral ulcers appeared, which have not improved. He denies any trouble breathing, pruritus, hemoptysis, hematochezia, or similar symptoms in the past. Past medical history is significant for a recent methicillin-resistant staphylococcus aureus (MRSA) skin infection 2 weeks ago secondary to a laceration on his left leg for which he has been taking trimethoprim-sulfamethoxazole. No other current medications. The patient is afebrile, and his vital signs are within normal limits. Physical examination reveals multiple raised, erythematous, circular papules averaging 1–2 cm in diameter with a central bulla, as shown in the exhibit (see image below). The cutaneous lesions occupy < 10% of his total body surface area (BSA). Nikolsky sign is negative. Multiple mucosal erosions are noted in the oral cavity. Generalized lymphadenopathy is present. A well-healing laceration is present on the left leg with no evidence of drainage or fluctuance. A cutaneous punch biopsy of one of the lesions is performed. Which of the following histopathologic features would most likely be found on this patient's biopsy?
A. Presence of intradermal blister and separation of suprabasal epidermal cells from basal cells
B. Rich dermal inflammatory infiltrate, predominantly composed of CD4+ T cells (Correct Answer)
C. Mucin deposition in the dermal layer
D. Scant dermal inflammatory infiltrate, predominantly composed of macrophages and dendritic cells
E. Presence of a subepidermal blister and a polymorphous inflammatory infiltrate with an eosinophilic predominance
Explanation: **Rich dermal inflammatory infiltrate, predominantly composed of CD4+ T cells**
- This patient's presentation with **painful oral ulcers**, a **targetoid rash** with central bullae covering <10% BSA, and a history of recent **trimethoprim-sulfamethoxazole** use strongly suggests **erythema multiforme (EM)**.
- Histologically, EM is characterized by a **dense perivascular lymphocytic infiltrate** in the superficial dermis, primarily consisting of **CD4+ T cells**, leading to **epidermal necrosis** and sometimes subepidermal blistering.
*Presence of intradermal blister and separation of suprabasal epidermal cells from basal cells*
- This description is characteristic of **pemphigus vulgaris**, an autoimmune bullous disease where **autoantibodies target desmoglein 3** and 1, causing **acantholysis** (loss of cell-to-cell adhesion) above the basal layer.
- Pemphigus vulgaris typically presents with **flaccid bullae** that easily rupture, forming erosions, and a **positive Nikolsky sign**, which is absent in this patient.
*Mucin deposition in the dermal layer*
- **Mucin deposition** in the dermis is a hallmark of certain conditions like **lupus erythematosus (especially subacute cutaneous lupus)**, **scleromyxedema**, or **pretibial myxedema**.
- These conditions do not typically present with the acute targetoid lesions and oral ulcerations seen here, and the clinical picture does not align with significant mucin deposition as a primary finding.
*Scant dermal inflammatory infiltrate, predominantly composed of macrophages and dendritic cells*
- A **scant inflammatory infiltrate** with macrophages and dendritic cells is not typical for an acute inflammatory condition like erythema multiforme.
- EM involves a **robust immune response** with a dense lymphocytic infiltrate contributing to epidermal damage.
*Presence of a subepidermal blister and a polymorphous inflammatory infiltrate with an eosinophilic predominance*
- Although **subepidermal blistering** can occur in severe EM, a **polymorphous inflammatory infiltrate with eosinophilic predominance** is more characteristic of conditions like **bullous pemphigoid** or various drug-induced eruptions that might feature significant eosinophilia.
- Bullous pemphigoid typically affects older individuals with tense bullae and severe pruritus, distinguishing it from this patient's presentation.
Question 30: 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**.
