A previously healthy, 16-year-old boy is brought to the emergency department with persistent bleeding from his gums after an elective removal of an impacted tooth. Multiple gauze packs were applied with minimal effect. He has a history of easy bruising. His family history is unremarkable except for a maternal uncle who had a history of easy bruising and joint swelling. Laboratory studies show:
Hematocrit 36%
Platelet count 170,000/mm3
Prothrombin time 13 sec
Partial thromboplastin time 65 sec
Bleeding time 5 min
Peripheral blood smear shows normal-sized platelets. Which of the following is the most likely diagnosis?
Q72
A 6-year-old boy is brought to the pediatrician by his mother after he reported having red urine. He has never experienced this before and did not eat anything unusual before the episode. His past medical history is notable for sensorineural deafness requiring hearing aids. He is otherwise healthy and enjoys being in the 1st grade. His birth history was unremarkable. His temperature is 98.8°F (37.1°C), blood pressure is 145/85 mmHg, pulse is 86/min, and respirations are 18/min. On examination, he is a well-appearing boy in no acute distress. Cardiac, respiratory, and abdominal exams are normal. A urinalysis is notable for microscopic hematuria and mild proteinuria. This patient’s condition is most commonly caused by which of the following inheritance patterns?
Q73
A 7-year-old girl presents with fatigue, jaundice, pruritus, and frequent pale stools. She developed these symptoms gradually over the past 3 months. Her past medical history is significant for multiple episodes of bronchitis and pneumonia. When asked about current respiratory symptoms, she says that she sometimes feels short of breath and has a dry, non-productive cough. Her mother was diagnosed with chronic obstructive pulmonary disease at age of 27. The girl's blood pressure is 110/80 mm Hg, the heart rate is 107/min, the respiratory rate is 18/min, and the temperature is 36.9°C (98.4°F). On physical examination, the patient is jaundiced with several petechiae over the inner surface of her upper and lower extremities. On auscultation, lung sounds are diminished and occasional wheezes are heard over the lower pulmonary lobes bilaterally. Heart auscultation reveals muffled heart sounds and no murmurs. On palpation, there is tenderness in the right upper quadrant of the abdomen and hepatomegaly. Her chest X-ray shows bilateral lower lobe emphysema. Which microscopic pathological changes are most characteristic of the patient’s condition?
Q74
A 21-year-old man comes to the emergency department because of a 2-week history of progressive shortness of breath and intermittent cough with blood-tinged sputum. During this time, he has also noticed blood in his urine. He has no history of serious illness and does not take any medications. His temperature is 37°C (98.6°F), pulse is 92/min, respirations are 28/min, and blood pressure is 152/90 mm Hg. Cardiopulmonary examination shows crackles at both lung bases. Urinalysis is positive for blood and results of a direct enzyme-linked immunoassay are positive for anti-GBM antibodies. The pathogenesis of this patient's disease is most similar to which of the following?
Q75
A 56-year-old man presents with feelings of anxiety and fatigue for the past 4 months. He says that he has also had some weight loss, as well as occasional double vision and a gritty sensation in his eyes for the last 2 months, which is worse at the end of the day. He has also noticed some painless swelling in his fingers and lower legs during the same time period. The patient denies any recent history of fevers, chills, night sweats, nausea, or vomiting. Current medications include aspirin, simvastatin, and omeprazole. Which of the following mechanisms is most likely responsible for this patient’s condition?
Q76
A 46-year-old Caucasian female presents with cold intolerance, weight gain, and constipation. She has also noticed that her nails have become thinner recently but denies any fever or neck pain. Which of the following is NOT an expected histological finding in the thyroid?
Q77
A 51-year-old man presents to the clinic with a history of hematuria and hemoptysis following pneumonia several weeks ago. He works as a hotel bellhop. His medical history is significant for gout, hypertension, hypercholesterolemia, diabetes mellitus type II, and mild intellectual disability. He currently smokes 2 packs of cigarettes per day and denies any alcohol use or any illicit drug use. His vital signs include: temperature 36.7°C (98.0°F), blood pressure 126/74 mm Hg, heart rate 87/min, and respiratory rate 23/min. Physical examination shows minimal bibasilar rales, but otherwise clear lungs on auscultation, grade 2/6 holosystolic murmur, and benign abdominal findings. Pulmonary function tests demonstrate a restrictive pattern and a current chest radiograph shows bibasilar alveolar infiltrates. Clinical pathology analysis reveals antiglomerular basement membrane antibody, and his renal biopsy shows a linear immunofluorescence pattern. Of the following options, which type of hypersensitivity reaction underlies this patient’s diagnosis?
Q78
A 6-year-old boy presents to his pediatrician accompanied by his mother for evaluation of a rash. The rash appeared a little over a week ago, and since that time the boy has felt tired. He is less interested in playing outside, preferring to remain indoors because his knees and stomach hurt. His past medical history is significant for an upper respiratory infection that resolved uneventfully without treatment 2 weeks ago. Temperature is 99.5°F (37.5°C), blood pressure is 115/70 mmHg, pulse is 90/min, and respirations are 18/min. Physical exam shows scattered maroon macules and papules on the lower extremities. The abdomen is diffusely tender to palpation. There is no cervical lymphadenopathy or conjunctival injection. Which of the following will most likely be found in this patient?
Q79
You are seeing an otherwise healthy 66-year-old male in clinic who is complaining of localized back pain and a new rash. On physical exam, his vital signs are within normal limits. You note a vesicular rash restricted to the upper left side of his back. In order to confirm your suspected diagnosis, you perform a diagnostic test. What would you expect to find on the diagnostic test that was performed?
Q80
A 36-year-old woman presents to the outpatient department with a recent onset of generalized weakness and weight gain. On physical examination, there is diffuse nontender enlargement of the thyroid gland. Fine-needle aspiration and cytology show lymphocytic infiltration with germinal centers and epithelial Hürthle cells. Which of the following autoantibodies is most likely to be found in this patient?
Systemic Pathology US Medical PG Practice Questions and MCQs
Question 71: A previously healthy, 16-year-old boy is brought to the emergency department with persistent bleeding from his gums after an elective removal of an impacted tooth. Multiple gauze packs were applied with minimal effect. He has a history of easy bruising. His family history is unremarkable except for a maternal uncle who had a history of easy bruising and joint swelling. Laboratory studies show:
Hematocrit 36%
Platelet count 170,000/mm3
Prothrombin time 13 sec
Partial thromboplastin time 65 sec
Bleeding time 5 min
Peripheral blood smear shows normal-sized platelets. Which of the following is the most likely diagnosis?
A. Hemophilia (Correct Answer)
B. Bernard-Soulier syndrome
C. Von Willebrand disease
D. Disseminated intravascular coagulation
E. Glanzmann thrombasthenia
Explanation: ***Hemophilia***
- The **prolonged partial thromboplastin time (PTT)** in the presence of a normal prothrombin time (PT) and platelet count strongly indicates an intrinsic pathway coagulation defect.
- The patient's history of **easy bruising**, persistent bleeding after dental extraction, and a **maternal uncle with a history of easy bruising and joint swelling** (suggesting hemarthroses) is classic for hemophilia, which is an **X-linked recessive** disorder.
*Bernard-Soulier syndrome*
- This condition involves a defect in the **GP Ib-IX-V receptor complex**, leading to impaired platelet adhesion.
- It would present with **thrombocytopenia (low platelet count)** and **abnormally large platelets** on a peripheral blood smear, neither of which are seen here.
*Von Willebrand disease*
- While it can cause easy bruising and prolonged bleeding, it typically results in a **prolonged bleeding time** due to defective platelet adhesion and sometimes a prolonged PTT (if factor VIII levels are significantly low).
- The patient's **normal bleeding time** and the clear family history of hemarthrosis-like symptoms in a maternal uncle make hemophilia more likely.
*Disseminated intravascular coagulation*
- This condition is characterized by widespread activation of clotting, leading to consumption of clotting factors and platelets.
- It would typically show **prolonged PT and PTT**, **thrombocytopenia**, and signs of microangiopathic hemolytic anemia, which are not present in this scenario.
*Glanzmann thrombasthenia*
- This is a rare **autosomal recessive** disorder characterized by a defect in the **GP IIb/IIIa receptor**, leading to impaired platelet aggregation.
- It presents with a **normal platelet count** but a **severely prolonged bleeding time**, which is not observed in this patient.
Question 72: A 6-year-old boy is brought to the pediatrician by his mother after he reported having red urine. He has never experienced this before and did not eat anything unusual before the episode. His past medical history is notable for sensorineural deafness requiring hearing aids. He is otherwise healthy and enjoys being in the 1st grade. His birth history was unremarkable. His temperature is 98.8°F (37.1°C), blood pressure is 145/85 mmHg, pulse is 86/min, and respirations are 18/min. On examination, he is a well-appearing boy in no acute distress. Cardiac, respiratory, and abdominal exams are normal. A urinalysis is notable for microscopic hematuria and mild proteinuria. This patient’s condition is most commonly caused by which of the following inheritance patterns?
A. X-linked dominant
B. Autosomal recessive
C. Autosomal dominant
D. X-linked recessive (Correct Answer)
E. Mitochondrial inheritance
Explanation: ***X-linked recessive***
- This is the **most common inheritance pattern** for **Alport syndrome**, accounting for approximately **80-85% of all cases**.
- This inheritance pattern is characteristic of **Alport syndrome**, which classically presents with **hematuria**, **sensorineural hearing loss**, and ocular abnormalities.
- The patient's presentation with **red urine (hematuria)** and a history of **sensorineural deafness** strongly points to **Alport syndrome**, which is primarily caused by **X-linked recessive** inheritance due to mutations in the *COL4A5* gene encoding the alpha-5 chain of type IV collagen.
- Males with the mutation are typically more severely affected, while female carriers may have variable manifestations.
*X-linked dominant*
- While Alport syndrome can manifest in females with an X-linked dominant-like pattern (due to mosaicism or severely affected carrier females), the **classic and most common inheritance** for severe forms in males is **X-linked recessive**.
- Conditions like **Fragile X syndrome** or **Vitamin D-resistant rickets** are examples of X-linked dominant conditions, but they do not typically present with the specific triad observed here.
*Autosomal recessive*
- An autosomal recessive form of **Alport syndrome** exists, but it accounts for only approximately **10-15% of cases** compared to the X-linked recessive form.
- While other conditions with **renal and auditory involvement** can be autosomal recessive (e.g., specific forms of branchio-oto-renal syndrome), the **combination of hematuria and sensorineural deafness with significant renal progression risk** in a male points most strongly to the X-linked form.
*Autosomal dominant*
- Alport syndrome also has an **autosomal dominant** form, which is typically due to mutations in *COL4A3* or *COL4A4* genes, but it accounts for only approximately **5% of cases** and is **less common** than the X-linked recessive form.
- The autosomal dominant form often presents with a **later onset** and a **more variable phenotype** with milder disease progression.
- While some forms of **polycystic kidney disease** are autosomal dominant and can cause hematuria, they typically involve cyst formation, which is not suggested by the clinical picture here.
*Mitochondrial inheritance*
- This inheritance pattern is associated with disorders affecting **energy production**, commonly involving multiple organ systems, including muscle, brain, and eye.
- While some mitochondrial disorders can affect the kidneys or cause hearing impairment, the **specific combination of hematuria and sensorineural deafness** as the primary presentation in this context is not characteristic of mitochondrial inheritance.
Question 73: A 7-year-old girl presents with fatigue, jaundice, pruritus, and frequent pale stools. She developed these symptoms gradually over the past 3 months. Her past medical history is significant for multiple episodes of bronchitis and pneumonia. When asked about current respiratory symptoms, she says that she sometimes feels short of breath and has a dry, non-productive cough. Her mother was diagnosed with chronic obstructive pulmonary disease at age of 27. The girl's blood pressure is 110/80 mm Hg, the heart rate is 107/min, the respiratory rate is 18/min, and the temperature is 36.9°C (98.4°F). On physical examination, the patient is jaundiced with several petechiae over the inner surface of her upper and lower extremities. On auscultation, lung sounds are diminished and occasional wheezes are heard over the lower pulmonary lobes bilaterally. Heart auscultation reveals muffled heart sounds and no murmurs. On palpation, there is tenderness in the right upper quadrant of the abdomen and hepatomegaly. Her chest X-ray shows bilateral lower lobe emphysema. Which microscopic pathological changes are most characteristic of the patient’s condition?
A. Widespread positive staining with Prussian blue
B. Extensive Congo-red positive deposits in the liver
C. Feathery degeneration of the hepatocytes
D. Extensive perisinusoidal fibrosis and hepatic venule dilation
E. Periodic acid-Schiff (PAS)-positive, diastase-resistant cytoplasmic granules in the hepatocytes (Correct Answer)
Explanation: ***Periodic acid-Schiff (PAS)-positive, diastase-resistant cytoplasmic granules in the hepatocytes***
- The patient's symptoms (pediatric **emphysema**, **jaundice**, **pruritus**, **hepatomegaly**, **bronchitis**, family history of early-onset COPD) are highly suggestive of **alpha-1 antitrypsin deficiency (A1AT)**.
- **A1AT deficiency** is characterized by the accumulation of misfolded alpha-1 antitrypsin protein within hepatocytes, which appears as **PAS-positive, diastase-resistant inclusions** on biopsy.
*Widespread positive staining with Prussian blue*
- **Prussian blue staining** is used to detect **iron deposits**, typically seen in conditions like **hemochromatosis**.
- This patient's presentation, including lung disease and early-onset liver disease, is not characteristic of iron overload.
*Extensive Congo-red positive cytoplasmic drops in the hepatocytes*
- **Congo-red staining** detects **amyloid deposits**, which are associated with conditions like **amyloidosis**.
- While amyloidosis can cause hepatomegaly, it typically doesn't present with pediatric emphysema or the specific liver/lung findings described.
*Feathery degeneration of the hepatocytes*
- **Feathery degeneration** is a characteristic microscopic finding in **cholestasis** and **bile duct obstruction**, often associated with **bile plugs** and portal inflammation.
- While the patient has cholestasis (jaundice, pruritus, pale stools), feathery degeneration is a histological consequence rather than the underlying primary pathological change seen in A1AT deficiency.
*Extensive perisinusoidal fibrosis and hepatic venule dilation*
- **Perisinusoidal fibrosis** and **hepatic venule dilation** can be seen in various forms of liver injury, including **alcoholic liver disease** or **veno-occlusive disease**.
- These findings are not specific to the underlying genetic defect in A1AT deficiency and do not explain the concomitant pulmonary involvement.
Question 74: A 21-year-old man comes to the emergency department because of a 2-week history of progressive shortness of breath and intermittent cough with blood-tinged sputum. During this time, he has also noticed blood in his urine. He has no history of serious illness and does not take any medications. His temperature is 37°C (98.6°F), pulse is 92/min, respirations are 28/min, and blood pressure is 152/90 mm Hg. Cardiopulmonary examination shows crackles at both lung bases. Urinalysis is positive for blood and results of a direct enzyme-linked immunoassay are positive for anti-GBM antibodies. The pathogenesis of this patient's disease is most similar to which of the following?
A. Henoch-Schönlein purpura
B. Autoimmune hemolytic anemia (Correct Answer)
C. Polyarteritis nodosa
D. Poststreptococcal glomerulonephritis
E. Graft versus host disease
Explanation: **Correct: Autoimmune hemolytic anemia**
- This patient presents with **Goodpasture syndrome**, an autoimmune disease characterized by **anti-glomerular basement membrane (GBM) antibodies** attacking both the kidneys (glomerulonephritis) and lungs (pulmonary hemorrhage).
- Autoimmune hemolytic anemia also involves **autoantibodies** (usually IgG or IgM) directly targeting and destroying host cells (red blood cells), representing a **type II hypersensitivity reaction** mediated by antibodies.
- Both conditions share the same pathogenic mechanism: direct autoantibody-mediated tissue/cell destruction.
*Incorrect: Henoch-Schönlein purpura*
- This is an **IgA-mediated vasculitis** primarily affecting small vessels, presenting with palpable purpura, abdominal pain, arthralgias, and IgA nephropathy.
- Its pathogenesis is distinctly different, involving **type III hypersensitivity** with IgA immune complex deposition rather than direct autoantibody attack on basement membranes.
*Incorrect: Polyarteritis nodosa*
- This is a **necrotizing vasculitis** of medium-sized arteries, which does not typically involve the glomerular capillaries directly or result in pulmonary hemorrhage.
- It is often associated with hepatitis B and presents with diverse systemic symptoms due to inflammation and necrosis of arterial walls, rather than autoantibodies against basement membranes.
*Incorrect: Poststreptococcal glomerulonephritis*
- This condition is an **immune complex-mediated (type III hypersensitivity) glomerulonephritis** that follows a streptococcal infection, characterized by granular deposits of C3 and IgG in the glomeruli.
- While it can cause hematuria and kidney damage, it does not involve anti-GBM antibodies or pulmonary hemorrhage, and its immune mechanism is distinct from type II hypersensitivity.
*Incorrect: Graft versus host disease*
- This is a complication of **allogeneic hematopoietic stem cell transplantation**, where donor T-cells attack host tissues.
- It is a **T-cell-mediated (type IV hypersensitivity) reaction**, entirely different from the autoantibody-mediated pathogenesis seen in Goodpasture syndrome.
Question 75: A 56-year-old man presents with feelings of anxiety and fatigue for the past 4 months. He says that he has also had some weight loss, as well as occasional double vision and a gritty sensation in his eyes for the last 2 months, which is worse at the end of the day. He has also noticed some painless swelling in his fingers and lower legs during the same time period. The patient denies any recent history of fevers, chills, night sweats, nausea, or vomiting. Current medications include aspirin, simvastatin, and omeprazole. Which of the following mechanisms is most likely responsible for this patient’s condition?
A. Autoantibody stimulation of a receptor (Correct Answer)
B. Autoantibodies resulting in tissue destruction
C. Excessive exogenous hormone use
D. Mutation in a receptor resulting in focal hyperfunctioning
E. Infiltration of tissue by neoplastic cells
Explanation: **Autoantibody stimulation of a receptor**
- The patient's symptoms of anxiety, fatigue, weight loss, double vision, gritty eyes, and painless swelling (consistent with pretibial myxedema) are classic for **hyperthyroidism**, specifically **Graves' disease**.
- In Graves' disease, stimulating **autoantibodies** (thyroid-stimulating immunoglobulins, TSI) bind to and activate the **TSH receptor** on thyroid follicular cells, leading to excessive thyroid hormone production.
*Autoantibodies resulting in tissue destruction*
- This mechanism is characteristic of **Hashimoto's thyroiditis**, where autoantibodies and cytotoxic T lymphocytes destroy thyroid tissue, leading to **hypothyroidism**.
- The patient's symptoms of weight loss, anxiety, and double vision (exophthalmos) are not consistent with hypothyroidism.
*Excessive exogenous hormone use*
- While excessive **exogenous thyroid hormone use** can cause hyperthyroidism, there is no indication in the patient's history of such use.
- Furthermore, the presence of **ophthalmopathy** and **pretibial myxedema** strongly suggests an autoimmune etiology like Graves' disease rather than drug-induced hyperthyroidism.
*Mutation in a receptor resulting in focal hyperfunctioning*
- This mechanism refers to conditions like **toxic thyroid adenoma** or **multinodular goiter** with autonomously functioning nodules, where somatic mutations in the TSH receptor lead to focal hyperactivity.
- While these can cause hyperthyroidism, they typically do not present with the diffuse ophthalmopathy and pretibial myxedema seen in Graves' disease with stimulating autoantibodies.
*Infiltration of tissue by neoplastic cells*
- **Neoplastic infiltration** of the thyroid gland (e.g., thyroid cancer) can sometimes lead to hyperthyroidism (though rare) or cause goiter.
- However, the specific constellation of symptoms including exophthalmos and pretibial myxedema is not typical for thyroid malignancy and is highly indicative of Graves' disease.
Question 76: A 46-year-old Caucasian female presents with cold intolerance, weight gain, and constipation. She has also noticed that her nails have become thinner recently but denies any fever or neck pain. Which of the following is NOT an expected histological finding in the thyroid?
A. Hurthle cells
B. Lymphocytic infiltration
C. Multinucleate giant cells (Correct Answer)
D. Several germinal centers
E. Fibrosis
Explanation: ***Multinucleate giant cells***
- The patient's symptoms (cold intolerance, weight gain, constipation, thin nails) are highly suggestive of **hypothyroidism**, most commonly caused by **Hashimoto's thyroiditis**.
- **Multinucleate giant cells** are typically associated with **subacute granulomatous (de Quervain's) thyroiditis**, which presents with painful thyroid enlargement and a biphasic course (transient hyperthyroidism followed by hypothyroidism).
*Hurthle cells*
- These are **eosinophilic, granular follicular cells** that represent metaplastic changes within the thyroid.
- They are a common histological finding in **Hashimoto's thyroiditis**, often seen alongside chronic inflammation.
*Lymphocytic infiltration*
- This is a hallmark feature of **Hashimoto's thyroiditis**, characterized by extensive infiltration of the thyroid parenchyma by **lymphocytes**, plasma cells, and macrophages.
- The immune response targets thyroid peroxidases and thyroglobulin, leading to gradual destruction of thyroid follicles.
*Several germinal centers*
- The presence of **germinal centers** within the thyroid is a characteristic histopathological feature of **Hashimoto's thyroiditis**.
- These centers indicate active B-cell proliferation and are part of the autoimmune process in the gland.
*Fibrosis*
- Over time, chronic inflammation in **Hashimoto's thyroiditis** often leads to **fibrosis** within the thyroid gland.
- Extensive fibrosis can result in a firm, enlarged thyroid and contribute to impaired thyroid function.
Question 77: A 51-year-old man presents to the clinic with a history of hematuria and hemoptysis following pneumonia several weeks ago. He works as a hotel bellhop. His medical history is significant for gout, hypertension, hypercholesterolemia, diabetes mellitus type II, and mild intellectual disability. He currently smokes 2 packs of cigarettes per day and denies any alcohol use or any illicit drug use. His vital signs include: temperature 36.7°C (98.0°F), blood pressure 126/74 mm Hg, heart rate 87/min, and respiratory rate 23/min. Physical examination shows minimal bibasilar rales, but otherwise clear lungs on auscultation, grade 2/6 holosystolic murmur, and benign abdominal findings. Pulmonary function tests demonstrate a restrictive pattern and a current chest radiograph shows bibasilar alveolar infiltrates. Clinical pathology analysis reveals antiglomerular basement membrane antibody, and his renal biopsy shows a linear immunofluorescence pattern. Of the following options, which type of hypersensitivity reaction underlies this patient’s diagnosis?
A. Type I and IV–mixed anaphylactic and cell-mediated hypersensitivity reaction
B. Type IV–cell-mediated (delayed) hypersensitivity reaction
C. Type I–anaphylactic hypersensitivity reaction
D. Type III–immune complex-mediated hypersensitivity reaction
E. Type II–cytotoxic hypersensitivity reaction (Correct Answer)
Explanation: ***Type II–cytotoxic hypersensitivity reaction***
- The presence of **antiglomerular basement membrane (anti-GBM) antibodies** targeting kidney and lung tissues (causing hematuria and hemoptysis) is characteristic of **Goodpasture syndrome**, which is a classic example of a **Type II hypersensitivity reaction**.
- In Type II reactions, antibodies (IgG or IgM) bind to antigens on the surface of cells or within tissues, leading to **complement activation** and cell destruction (cytotoxicity) or dysfunction.
*Type I and IV–mixed anaphylactic and cell-mediated hypersensitivity reaction*
- This option describes a mixed reaction that doesn't fit the clinical picture of **anti-GBM disease**. Type I involves IgE-mediated mast cell degranulation, and Type IV involves T-cell-mediated delayed responses.
- While infections often precede Goodpasture syndrome, the direct pathology from **anti-GBM antibodies** is distinct from typical mixed allergic or delayed-type reactions.
*Type IV–cell-mediated (delayed) hypersensitivity reaction*
- Type IV reactions are characterized by **T-cell-mediated inflammation** and do not involve antibodies binding to tissue antigens; examples include tuberculosis skin tests or contact dermatitis.
- The presence of specific **anti-GBM antibodies** and a **linear immunofluorescence pattern** on renal biopsy clearly indicate an antibody-mediated process, ruling out a purely cell-mediated reaction.
*Type I–anaphylactic hypersensitivity reaction*
- Type I reactions involve **IgE antibodies** binding to mast cells and basophils, leading to histamine release and immediate allergic responses like anaphylaxis, asthma, or hives.
- The symptoms of hematuria and hemoptysis due to **glomerular basement membrane damage** are inconsistent with an immediate IgE-mediated allergic reaction.
*Type III–immune complex-mediated hypersensitivity reaction*
- Type III reactions involve the formation of **soluble immune complexes** (antigen-antibody complexes) that deposit in tissues, leading to inflammation (e.g., lupus nephritis, serum sickness).
- While antibodies are involved, the defining feature of Goodpasture syndrome is antibodies directly targeting and binding to fixed antigens on the **glomerular and alveolar basement membranes**, not circulating immune complex deposition, which would typically show a **granular immunofluorescence pattern**.
Question 78: A 6-year-old boy presents to his pediatrician accompanied by his mother for evaluation of a rash. The rash appeared a little over a week ago, and since that time the boy has felt tired. He is less interested in playing outside, preferring to remain indoors because his knees and stomach hurt. His past medical history is significant for an upper respiratory infection that resolved uneventfully without treatment 2 weeks ago. Temperature is 99.5°F (37.5°C), blood pressure is 115/70 mmHg, pulse is 90/min, and respirations are 18/min. Physical exam shows scattered maroon macules and papules on the lower extremities. The abdomen is diffusely tender to palpation. There is no cervical lymphadenopathy or conjunctival injection. Which of the following will most likely be found in this patient?
A. Coronary artery aneurysms
B. Leukocytoclastic vasculitis (Correct Answer)
C. Thrombocytopenia
D. Mitral regurgitation
E. Occult malignancy
Explanation: ***Leukocytoclastic vasculitis***
- This patient presents with symptoms highly suggestive of **Henoch-Schönlein Purpura (HSP)**, including a preceding URI, fatigue, low-grade fever, **abdominal pain**, and a **palpable purpura** primarily on the lower extremities.
- HSP is characterized by IgA-mediated **small-vessel vasculitis**, which histologically presents as leukocytoclastic vasculitis with IgA deposition on immunofluorescence.
*Coronary artery aneurysms*
- **Coronary artery aneurysms** are a classic complication of **Kawasaki disease**, not Henoch-Schönlein Purpura.
- Kawasaki disease presents with different clinical features, including prolonged fever, conjunctival injection, oral changes, and cervical lymphadenopathy.
*Thrombocytopenia*
- **Thrombocytopenia** is characterized by a low platelet count and often presents with petechiae, purpura, and bleeding, but the rash in HSP is due to inflammation and extravasation of red blood cells, not low platelets.
- Platelet counts in HSP are typically **normal** or can be slightly elevated as an acute phase reactant.
*Mitral regurgitation*
- **Mitral regurgitation** is a common manifestation of **rheumatic fever**, particularly after recurrent episodes, caused by valvular damage.
- Rheumatic fever is also preceded by infection (Group A Strep) but involves different symptoms like migratory polyarthritis, carditis, chorea, erythema marginatum, and subcutaneous nodules, which are not described here.
*Occult malignancy*
- While an **occult malignancy** can cause paraneoplastic syndromes or constitutional symptoms, the specific constellation of symptoms, including the migratory rash, abdominal pain, and preceding URI, points much more strongly to **HSP** in a 6-year-old.
- The presentation is more consistent with an acute, inflammatory process rather than a chronic, insidious malignant one.
Question 79: You are seeing an otherwise healthy 66-year-old male in clinic who is complaining of localized back pain and a new rash. On physical exam, his vital signs are within normal limits. You note a vesicular rash restricted to the upper left side of his back. In order to confirm your suspected diagnosis, you perform a diagnostic test. What would you expect to find on the diagnostic test that was performed?
A. Gram negative bacilli
B. Branching pseudohyphae
C. Pear shaped motile cells
D. Multinucleated giant cells (Correct Answer)
E. Gram positive cocci
Explanation: ***Multinucleated giant cells***
- The patient's presentation of a **unilateral, vesicular rash** in an older adult, along with localized back pain, is highly suggestive of **herpes zoster (shingles)**.
- A Tzanck smear, a common diagnostic test for vesicular lesions, would reveal **multinucleated giant cells** and **intranuclear inclusions**, characteristic cytopathic effects of herpesviruses like VZV.
*Gram negative bacilli*
- This finding would suggest a **bacterial infection**, typically not associated with vesicular rashes like shingles.
- Gram-negative bacilli are often implicated in conditions such as **urinary tract infections** or **sepsis**, not dermatological viral infections.
*Branching pseudohyphae*
- This microscopic feature is characteristic of **fungal infections**, specifically **Candida species**, which present as a candidiasis rash, not a dermatomal vesicular rash.
- Fungal rashes are typically erythematous and can be pruritic but do not usually form discrete vesicles in a dermatomal distribution.
*Pear shaped motile cells*
- This describes **Trichomonas vaginalis**, a parasite causing sexually transmitted infections, primarily **vaginitis** or **urethritis**.
- This finding would be completely unrelated to a vesicular skin rash or the suspected diagnosis of shingles.
*Gram positive cocci*
- This finding is indicative of a **bacterial infection**, such as those caused by **Staphylococcus aureus** or **Streptococcus pyogenes**.
- While these bacteria can cause skin infections (e.g., impetigo, cellulitis), they do not produce the classic unilateral vesicular rash of shingles and would not involve multinucleated giant cells on microscopy.
Question 80: A 36-year-old woman presents to the outpatient department with a recent onset of generalized weakness and weight gain. On physical examination, there is diffuse nontender enlargement of the thyroid gland. Fine-needle aspiration and cytology show lymphocytic infiltration with germinal centers and epithelial Hürthle cells. Which of the following autoantibodies is most likely to be found in this patient?
A. Anti-TSH receptor antibody
B. Antihistone antibody
C. Antimitochondrial antibody
D. Anti-parietal cell antibody
E. Anti-thyroid peroxidase (anti-TPO) antibody (Correct Answer)
Explanation: ***Anti-thyroid peroxidase (anti-TPO) antibody***
- The clinical presentation of **generalized weakness, weight gain**, and **diffuse nontender thyroid enlargement** points towards **hypothyroidism**, likely due to **Hashimoto's thyroiditis**.
- **Fine-needle aspiration** findings of **lymphocytic infiltration with germinal centers** and **Hürthle cells** are classic for Hashimoto's, which is an autoimmune condition primarily mediated by **anti-TPO antibodies**.
*Anti-TSH receptor antibody*
- These antibodies are characteristic of **Graves' disease**, an autoimmune disorder causing **hyperthyroidism**, which presents with weight loss and symptoms of increased metabolism, the opposite of this patient's presentation.
- They can be either stimulating (most common) or blocking, but their presence is strongly associated with **hyperthyroidism** and not the hypothyroid state suggested here.
*Antihistone antibody*
- This antibody is highly sensitive for **drug-induced lupus erythematosus** but can also be seen in systemic lupus erythematosus (SLE).
- It is not directly related to thyroid pathologies.
*Antimitochondrial antibody*
- This antibody is a hallmark of **primary biliary cholangitis (PBC)**, an autoimmune liver disease, and has no direct association with thyroid conditions.
- PBC typically presents with fatigue, pruritus, and elevated liver enzymes.
*Anti-parietal cell antibody*
- These antibodies are associated with **pernicious anemia**, an autoimmune condition leading to **vitamin B12 deficiency** due to malabsorption.
- While pernicious anemia can cause weakness, it does not explain the thyroid enlargement or the specific cytological findings in the thyroid.
