A 45-year-old man presents to the office with complaints of facial puffiness and mild swelling in his lower back. He denies chest pain, blood in the urine, or fever. He was recently diagnosed with colon cancer. The vital signs include a blood pressure of 122/78 mm Hg, a pulse of 76/min, a temperature of 36.9°C (98.4°F), and a respiratory rate of 10/min. On physical examination, there is mild facial puffiness that is pitting in nature and presacral edema. His other systemic findings are within normal limits.
Urinalysis shows:
pH 6.2
Color light yellow
RBC none
WBC 3–4/HPF
Protein 4+
Cast oval fat bodies
Glucose absent
Crystal none
Ketone absent
Nitrite absent
24 hours urine protein excretion 4.8 g
A renal biopsy is ordered and diffuse capillary and basement membrane thickening is noted. Which of the following findings is expected to be present if an electron microscopy of the biopsy sample is performed?
Q82
A 29-year-old man comes to the emergency department because of progressively worsening fatigue and shortness of breath for the past 2 weeks. His only medication is insulin. Examination shows elevated jugular venous distention and coarse crackles in both lungs. Despite appropriate life-saving measures, he dies. Gross examination of the heart at autopsy shows concentrically thickened myocardium and microscopic examination shows large cardiomyocytes with intracellular iron granules. Examination of the spinal cord shows atrophy of the lateral corticospinal tracts, spinocerebellar tracts, and dorsal columns. Which of the following is the most likely underlying cause of this patient's condition?
Q83
A 45-year-old man is brought to the hospital by his daughter with complaints of wide-based gait. His daughter reveals that he was sitting silently in the examination chair with a blank face. In addition, he was frequently talking to the empty chairs and told that his friends are sitting there. He has been forgetting many small things recently. On physical examination, fine movements are seen at resting condition that disappears when he is asked to drink water. A stepwise slowness in movement is also seen in his upper limb. Which of the following is most likely to be observed in the histological specimen of this patient?
Q84
A 65-year-old man comes to the physician because of a 6-month history of progressive fatigue and abdominal pain. Physical examination shows pale mucous membranes and splenomegaly. Hemoglobin concentration is 9.1 g/dL and leukocyte count is 3,400/mm3. Peripheral blood smear shows nucleated red blood cells and teardrop poikilocytosis. A Janus kinase 2 gene mutation is present. Which of the following is the most likely underlying mechanism of this patient's condition?
Q85
A 12-year-old boy presents to the emergency department with a recent history of easy bleeding. He experienced multiple episodes of epistaxis and bleeding gums over the past two days. He also had flu-like symptoms a week ago which resolved over the past few days. His past medical history is notable for well-controlled asthma. His temperature is 98.9°F (37°C). Physical examination is notable for a petechial rash. No splenomegaly is noted. A coagulation panel reveals an elevation in bleeding time with normal PT and PTT. The blood component that is most likely deficient in this patient contains granules of which of the following?
Q86
An 18-year-old African-American woman comes to the physician for the evaluation of worsening fatigue that started 1 year ago. Physical examination shows mild jaundice and splenomegaly. Laboratory studies show:
Hemoglobin 10.4 g/dL
Mean corpuscular hemoglobin concentration 43% Hb/cell
Platelet count 220,000/mm3
Reticulocyte count 7%
A peripheral blood smear shows target cells and erythrocytes with hemoglobin crystals. Which of the following is the most likely underlying cause of this patient's findings?
Q87
A 34-year-old female presents to her primary care physician with complaints of fevers, nausea/vomiting, and severe left flank pain that has developed over the past several hours. She denies any prior episodes similar to her current presentation. Physical examination is significant for a body temperature of 39.1 C and costovertebral angle tenderness. A urinalysis and urine microscopy are ordered. Which of the following findings on kidney histology would be expected in this patient?
Q88
A 12-year-old girl is presented to the office by her mother with complaints of cola-colored urine and mild facial puffiness that began 5 days ago. According to her mother, she had a sore throat 3 weeks ago. Her immunization records are up to date. The mother denies fever and any change in bowel habits. The vital signs include blood pressure 138/78 mm Hg, pulse 88/min, temperature 36.8°C (98.2°F), and respiratory rate 11/min. On physical examination, there is pitting edema of the upper and lower extremities bilaterally. An oropharyngeal examination is normal. Urinalysis shows the following results:
pH 6.2
Color dark brown
Red blood cell (RBC) count 18–20/HPF
White blood cell (WBC) count 3–4/HPF
Protein 1+
Cast RBC casts
Glucose absent
Crystal none
Ketone absent
Nitrite absent
24 h urine protein excretion 0.6 g
HPF: high-power field
Which of the following would best describe the light microscopy findings in this case?
Q89
A 7-year-old girl is brought to the physician with complaints of erythema and rashes over the bridge of her nose and on her forehead for the past 6 months. She also has vesiculobullous and erythematous scaly crusted lesions on the scalp and around the perioral areas. Her parents report a history of worsening symptoms during exposure to sunlight, along with a history of joint pain and oral ulcers. Her temperature is 38.6°C (101.4°F), pulse is 88/min, and respirations are 20/min. On physical examination, pallor and cervical lymphadenopathy are present. On cutaneous examination, diffuse hair loss and hyperpigmented scaly lesions are present. Her laboratory studies show:
Hemoglobin 7.9 mg/dL
Total leukocyte count 6,300/mm3
Platelet count 167,000/mm3
Erythrocyte sedimentation rate 30 mm/h
ANA titer 1:520 (positive)
Which of the following most likely explains the mechanism of this condition?
Q90
Physical exam of a 15-year-old female reveals impetigo around her mouth. A sample of the pus is taken and cultured. Growth reveals gram-positive cocci in chains that are bacitracin sensitive. Which of the following symptoms would be concerning for a serious sequela of this skin infection?
Systemic Pathology US Medical PG Practice Questions and MCQs
Question 81: A 45-year-old man presents to the office with complaints of facial puffiness and mild swelling in his lower back. He denies chest pain, blood in the urine, or fever. He was recently diagnosed with colon cancer. The vital signs include a blood pressure of 122/78 mm Hg, a pulse of 76/min, a temperature of 36.9°C (98.4°F), and a respiratory rate of 10/min. On physical examination, there is mild facial puffiness that is pitting in nature and presacral edema. His other systemic findings are within normal limits.
Urinalysis shows:
pH 6.2
Color light yellow
RBC none
WBC 3–4/HPF
Protein 4+
Cast oval fat bodies
Glucose absent
Crystal none
Ketone absent
Nitrite absent
24 hours urine protein excretion 4.8 g
A renal biopsy is ordered and diffuse capillary and basement membrane thickening is noted. Which of the following findings is expected to be present if an electron microscopy of the biopsy sample is performed?
A. Subepithelial humps
B. Effacement of foot process
C. Basket-weave appearance of GBM
D. Massive amyloid deposition and spicular aggregates
E. Spike and dome appearance (Correct Answer)
Explanation: ***Spike and dome appearance***
- The patient's presentation with **facial puffiness**, **presacral edema**, **4+ proteinuria**, **oval fat bodies**, and **4.8 g/24hr protein excretion** with **diffuse capillary and basement membrane thickening** on renal biopsy, in the setting of **colon cancer**, is highly suggestive of **membranous nephropathy**.
- **Membranous nephropathy** is characterized on electron microscopy by **subepithelial immune complex deposits**, which often manifest as a **"spike and dome" appearance** due to new basement membrane material laid down between the immune deposits.
*Subepithelial humps*
- **Subepithelial humps** are characteristic of **post-streptococcal glomerulonephritis** and other forms of **acute post-infectious glomerulonephritis**.
- This patient's presentation with **nephrotic syndrome** features and chronic disease does not align with acute glomerulonephritis.
*Effacement of foot process*
- **Effacement of foot processes** (podocyte effacement) is a finding seen in almost all causes of **heavy proteinuria** and **nephrotic syndrome**, including **minimal change disease**, **focal segmental glomerulosclerosis**, and **membranous nephropathy**.
- While it would be present in this case, it is a non-specific finding of proteinuria itself, not a defining characteristic of **membranous nephropathy** itself, which is what "spike and dome" is.
*Basket-weave appearance of GBM*
- The **"basket-weave" appearance** refers to the irregular thickening and lamellation of the **glomerular basement membrane (GBM)**, typically seen in **Alport syndrome**.
- This is a genetic disorder of type IV collagen and does not fit the clinical picture of an adult with recent colon cancer and acquired nephrotic syndrome.
*Massive amyloid deposition and spicular aggregates*
- **Massive amyloid deposition** with **spicular aggregates** is characteristic of **amyloidosis**.
- While amyloidosis can cause nephrotic syndrome and be associated with chronic diseases, the light microscopy finding of **diffuse capillary and basement membrane thickening** without specific mention of congophilic deposits or apple-green birefringence makes membranous nephropathy a more direct fit with the "spike and dome" EM finding.
Question 82: A 29-year-old man comes to the emergency department because of progressively worsening fatigue and shortness of breath for the past 2 weeks. His only medication is insulin. Examination shows elevated jugular venous distention and coarse crackles in both lungs. Despite appropriate life-saving measures, he dies. Gross examination of the heart at autopsy shows concentrically thickened myocardium and microscopic examination shows large cardiomyocytes with intracellular iron granules. Examination of the spinal cord shows atrophy of the lateral corticospinal tracts, spinocerebellar tracts, and dorsal columns. Which of the following is the most likely underlying cause of this patient's condition?
A. CTG trinucleotide repeat expansion on chromosome 19
B. SOD1 gene mutation on chromosome 21
C. SMN1 gene mutation on chromosome 5
D. GAA trinucleotide repeat expansion on chromosome 9 (Correct Answer)
E. Dystrophin gene mutation on the X chromosome
Explanation: ***GAA trinucleotide repeat expansion on chromosome 9***
- The patient's presentation with **hypertrophic cardiomyopathy** (concentrically thickened myocardium, large cardiomyocytes) and **neurological degeneration** affecting the **lateral corticospinal tracts, spinocerebellar tracts, and dorsal columns** is characteristic of **Friedreich ataxia**.
- **Friedreich ataxia** is caused by a **GAA trinucleotide repeat expansion** in the **FXN gene on chromosome 9**, leading to reduced frataxin protein and mitochondrial dysfunction.
*CTG trinucleotide repeat expansion on chromosome 19*
- This mutation is associated with **myotonic dystrophy type 1**, which presents with **myotonia**, muscle weakness, and often cardiac conduction abnormalities or dilated cardiomyopathy, but typically not hypertrophic cardiomyopathy or the specific spinal cord degeneration described.
- While cardiac involvement can occur, the neurological pattern of **spinal cord tract degeneration** and **hypertrophic cardiomyopathy** is not typical for myotonic dystrophy type 1.
*SOD1 gene mutation on chromosome 21*
- Mutations in the **SOD1 gene** are a common cause of **familial amyotrophic lateral sclerosis (ALS)**, characterized by progressive degeneration of upper and lower motor neurons.
- ALS primarily presents with muscle weakness, atrophy, and fasciculations, but does not typically involve **hypertrophic cardiomyopathy** or the specific pattern of **sensory tract degeneration** seen in this patient.
*SMN1 gene mutation on chromosome 5*
- This mutation causes **spinal muscular atrophy (SMA)**, a genetic disorder characterized by the loss of motor neurons in the spinal cord, leading to progressive muscle weakness and atrophy.
- SMA does not typically involve **hypertrophic cardiomyopathy** or the specific combination of motor and sensory tract degeneration described in the patient.
*Dystrophin gene mutation on the X chromosome*
- Mutations in the **dystrophin gene** cause **Duchenne and Becker muscular dystrophies**, which are characterized by progressive muscle weakness and **dilated cardiomyopathy**, not hypertrophic cardiomyopathy.
- While these disorders affect muscles, the specific pattern of **spinal cord tract atrophy** described is not a feature of dystrophinopathies.
Question 83: A 45-year-old man is brought to the hospital by his daughter with complaints of wide-based gait. His daughter reveals that he was sitting silently in the examination chair with a blank face. In addition, he was frequently talking to the empty chairs and told that his friends are sitting there. He has been forgetting many small things recently. On physical examination, fine movements are seen at resting condition that disappears when he is asked to drink water. A stepwise slowness in movement is also seen in his upper limb. Which of the following is most likely to be observed in the histological specimen of this patient?
A. Spongiform changes in cortex
B. Neuritic plaques in cortex
C. Lewy bodies in affected neurons (Correct Answer)
D. Tau protein aggregates in cortex
E. Neurofibrillary tangles in hippocampus
Explanation: ***Lewy bodies in affected neurons***
- The patient's symptoms of **wide-based gait**, **cognitive decline** (forgetting things, talking to empty chairs), **psychotic features** (visual hallucinations), and **motor symptoms** (resting tremor, bradykinesia) are highly suggestive of **Lewy body dementia** (LBD).
- **Lewy bodies**, which are abnormal aggregates of **alpha-synuclein protein**, are the characteristic histological finding in neurons of individuals with LBD, found in both **cortical areas** (defining feature of LBD) and **substantia nigra**.
- The presence of early prominent visual hallucinations with parkinsonism and cognitive fluctuations is pathognomonic for Lewy body dementia.
*Spongiform changes in cortex*
- This finding is characteristic of **prion diseases**, such as **Creutzfeldt-Jakob disease** (CJD), which typically present with rapidly progressive dementia and myoclonus.
- While CJD involves cognitive decline, the presence of resting tremor, visual hallucinations, and a more gradual progression with parkinsonian features makes spongiform changes unlikely.
*Neuritic plaques in cortex*
- **Neuritic plaques**, composed of **amyloid-beta protein**, are a hallmark of **Alzheimer's disease**.
- Although Alzheimer's disease causes cognitive decline, the prominent early motor symptoms (resting tremor, wide-based gait, bradykinesia) and early visual hallucinations are not typical features of Alzheimer's disease.
*Tau protein aggregates in cortex*
- **Tau protein aggregates** (neurofibrillary tangles) are another key histological feature of **Alzheimer's disease** and certain **tauopathies** like **frontotemporal dementia** and **progressive supranuclear palsy**.
- While associated with dementia, they do not explain the unique combination of early parkinsonian motor features and prominent visual hallucinations seen in this patient.
*Neurofibrillary tangles in hippocampus*
- **Neurofibrillary tangles** composed of hyperphosphorylated **tau protein** in the hippocampus are characteristic of **Alzheimer's disease** and correlate with memory impairment.
- However, Alzheimer's disease does not typically present with early parkinsonism, resting tremor, or prominent visual hallucinations as seen in this patient with Lewy body dementia.
Question 84: A 65-year-old man comes to the physician because of a 6-month history of progressive fatigue and abdominal pain. Physical examination shows pale mucous membranes and splenomegaly. Hemoglobin concentration is 9.1 g/dL and leukocyte count is 3,400/mm3. Peripheral blood smear shows nucleated red blood cells and teardrop poikilocytosis. A Janus kinase 2 gene mutation is present. Which of the following is the most likely underlying mechanism of this patient's condition?
A. Elevated levels of circulating hepcidin
B. Lymphocytic infiltration of reticuloendothelial system
C. Viral replication in lymphoid cells
D. Fibrosis in the bone marrow (Correct Answer)
E. Translocation between chromosome 9 and 22
Explanation: ***Fibrosis in the bone marrow***
- The constellation of **fatigue**, **anemia** (Hb 9.1 g/dL), **splenomegaly**, **teardrop poikilocytosis**, and a **JAK2 mutation** is highly suggestive of **primary myelofibrosis**.
- **Bone marrow fibrosis** is the hallmark of primary myelofibrosis, leading to ineffective hematopoiesis and extramedullary hematopoiesis (causing splenomegaly).
*Elevated levels of circulating hepcidin*
- **Elevated hepcidin** is characteristic of **anemia of chronic disease** or **iron-refractory iron deficiency anemia**, where iron is trapped in macrophages despite adequate stores.
- While anemia is present, the other features (splenomegaly, teardrop cells, JAK2 mutation) are not consistent with anemia of chronic disease as the primary mechanism.
*Lymphocytic infiltration of reticuloendothelial system*
- **Lymphocytic infiltration** is typical of **lymphoproliferative disorders** like leukemias or lymphomas, which would present with different CBC findings, not primarily myelofibrosis features.
- This mechanism would lead to different peripheral smear findings (e.g., lymphocytosis) rather than nucleated red cells and teardrop cells.
*Viral replication in lymphoid cells*
- **Viral replication in lymphoid cells** can cause various hematologic abnormalities (e.g., infectious mononucleosis, some lymphomas), but it is not the underlying mechanism for the specific features of primary myelofibrosis.
- This would not explain the **JAK2 mutation** or the characteristic **bone marrow fibrosis** and **extramedullary hematopoiesis**.
*Translocation between chromosome 9 and 22*
- A **translocation between chromosome 9 and 22** (the **Philadelphia chromosome**) is characteristic of **chronic myeloid leukemia (CML)**.
- While CML can cause splenomegaly and myeloid abnormalities, it typically presents with marked leukocytosis and does not feature the prominent teardrop cells or the primary myelofibrosis features seen here; CML is characterized by the **BCR-ABL1 fusion gene**, not primarily a JAK2 mutation.
Question 85: A 12-year-old boy presents to the emergency department with a recent history of easy bleeding. He experienced multiple episodes of epistaxis and bleeding gums over the past two days. He also had flu-like symptoms a week ago which resolved over the past few days. His past medical history is notable for well-controlled asthma. His temperature is 98.9°F (37°C). Physical examination is notable for a petechial rash. No splenomegaly is noted. A coagulation panel reveals an elevation in bleeding time with normal PT and PTT. The blood component that is most likely deficient in this patient contains granules of which of the following?
A. Myeloperoxidase
B. Heparin
C. Tryptase
D. Major basic protein
E. von Willebrand factor (Correct Answer)
Explanation: ***von Willebrand factor***
- This patient's presentation with **easy bleeding** (epistaxis, bleeding gums), **petechial rash**, and a history of a recent **viral infection** followed by normal PT/PTT but **elevated bleeding time** is highly suggestive of **Immune Thrombocytopenic Purpura (ITP)**.
- In ITP, antibodies attack **platelets**, leading to their destruction and a deficiency. Platelet alpha-granules contain **von Willebrand factor**, platelet factor 4, and fibrinogen, which are crucial for hemostasis.
*Myeloperoxidase*
- **Myeloperoxidase** is found in the **azurophilic granules** of neutrophils and monocytes, not platelets, and is involved in microbial killing.
- A deficiency in myeloperoxidase would primarily impair immune function rather than cause a bleeding disorder with elevated bleeding time.
*Heparin*
- **Heparin** is an anticoagulant found primarily in the granules of **mast cells** and basophils, which are involved in allergic reactions and inflammation.
- Heparin is not a component of platelet granules, and its deficiency would lead to increased clotting, not bleeding.
*Tryptase*
- **Tryptase** is an enzyme found in the granules of **mast cells**, released during allergic reactions and anaphylaxis.
- It is not associated with platelet function or the type of bleeding disorder described here.
*Major basic protein*
- **Major basic protein (MBP)** is a cytotoxic protein found in the granules of **eosinophils**, primarily involved in defense against parasitic infections.
- Its presence or absence is unrelated to platelet function or this patient's bleeding symptoms.
Question 86: An 18-year-old African-American woman comes to the physician for the evaluation of worsening fatigue that started 1 year ago. Physical examination shows mild jaundice and splenomegaly. Laboratory studies show:
Hemoglobin 10.4 g/dL
Mean corpuscular hemoglobin concentration 43% Hb/cell
Platelet count 220,000/mm3
Reticulocyte count 7%
A peripheral blood smear shows target cells and erythrocytes with hemoglobin crystals. Which of the following is the most likely underlying cause of this patient's findings?
A. Acquired mutation of membrane-bound glycosylphosphatidylinositol anchor
B. Decreased conversion of oxidized glutathione into its reduced form
C. Replacement of glutamate by valine in beta-globin chain
D. Replacement of glutamate by lysine in beta-globin chain (Correct Answer)
E. Reduced production of beta-globin due to a mutation in the HbB gene
Explanation: ***Replacement of glutamate by lysine in beta-globin chain***
- The combination of **mild jaundice**, **splenomegaly**, **anemia**, **elevated reticulocyte count**, and the presence of **target cells** and **hemoglobin C crystals** on peripheral smear is characteristic of **Hemoglobin C disease**.
- **Hemoglobin C** results from the **replacement of glutamate by lysine at position 6 of the beta-globin chain**, leading to abnormal hemoglobin and erythrocyte morphology.
*Acquired mutation of membrane-bound glycosylphosphatidylinositol anchor*
- This describes **Paroxysmal Nocturnal Hemoglobinuria (PNH)**, which is characterized by **hemolytic anemia**, **thrombosis**, and **bone marrow failure**.
- While it causes hemolytic anemia, the peripheral smear findings of **target cells** and **hemoglobin crystals** are not typical for PNH as seen in this patient.
*Decreased conversion of oxidized glutathione into its reduced form*
- This mechanism is characteristic of **Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency**, a cause of **hemolytic anemia**.
- G6PD deficiency typically presents with episodic hemolysis triggered by **oxidative stress**, and the characteristic peripheral smear findings are **Heinz bodies** and **bite cells**, not hemoglobin crystals.
*Replacement of glutamate by valine in beta-globin chain*
- This mutation describes **Sickle Cell Anemia**, which also causes hemolytic anemia and splenomegaly.
- While it leads to **sickle cells** on peripheral smear, **hemoglobin C crystals** and **target cells** are not the primary features; sickle cells and Howell-Jolly bodies would be expected.
*Reduced production of beta-globin due to a mutation in the HbB gene*
- This describes **Beta-thalassemia**, a group of disorders characterized by **reduced or absent beta-globin chain synthesis**.
- Beta-thalassemia typically presents with **microcytic hypochromic anemia** and **target cells**, but the presence of **hemoglobin C crystals** is not a feature.
Question 87: A 34-year-old female presents to her primary care physician with complaints of fevers, nausea/vomiting, and severe left flank pain that has developed over the past several hours. She denies any prior episodes similar to her current presentation. Physical examination is significant for a body temperature of 39.1 C and costovertebral angle tenderness. A urinalysis and urine microscopy are ordered. Which of the following findings on kidney histology would be expected in this patient?
A. Enlarged, hypercellular glomeruli with 'wire-looping' of capillaries
B. Neutrophils filling the lumens of the renal tubules (Correct Answer)
C. Scarring of the glomeruli
D. Interstitial fibrosis and lymphocytic infiltrate
E. Thickening of the capillaries and glomerular basement membrane
Explanation: ***Neutrophils filling the lumens of the renal tubules***
- This patient's symptoms (fevers, nausea/vomiting, severe left flank pain, fever, and costovertebral angle tenderness) are highly suggestive of **acute pyelonephritis**, an infection of the kidney parenchyma.
- Histologically, acute pyelonephritis is characterized by an acute inflammatory infiltrate, primarily **neutrophils**, within the **renal tubules** and interstitial tissue, often forming **abscesses**.
*Enlarged, hypercellular glomeruli with 'wire-looping' of capillaries*
- This description is characteristic of **diffuse proliferative glomerulonephritis**, often associated with conditions like **systemic lupus erythematosus (SLE)**.
- The clinical presentation of sudden-onset severe flank pain and fever is not typical for glomerulonephritis, which usually presents with hematuria, proteinuria, and edema.
*Scarring of the glomeruli*
- **Glomerulosclerosis** (scarring of the glomeruli) is a feature of chronic kidney disease and various chronic glomerular disorders, not acute pyelonephritis.
- Patients with glomerular scarring typically present with signs of chronic kidney injury, such as persistent proteinuria and declining renal function, rather than acute infectious symptoms.
*Interstitial fibrosis and lymphocytic infiltrate*
- This is a hallmark of **chronic interstitial nephritis**, which can be caused by long-term drug use, autoimmune diseases, or chronic obstructive uropathy.
- While lymphocytes indicate inflammation, the presence of fibrosis suggests a chronic process, differing from the acute bacterial infection seen in pyelonephritis.
*Thickening of the capillaries and glomerular basement membrane*
- This finding is suggestive of various glomerular diseases, such as **membranous nephropathy** or **diabetic nephropathy**, where the glomerular basement membrane is significantly altered.
- Such conditions typically manifest with proteinuria and nephrotic or nephritic syndromes, not the acute infectious symptoms described.
Question 88: A 12-year-old girl is presented to the office by her mother with complaints of cola-colored urine and mild facial puffiness that began 5 days ago. According to her mother, she had a sore throat 3 weeks ago. Her immunization records are up to date. The mother denies fever and any change in bowel habits. The vital signs include blood pressure 138/78 mm Hg, pulse 88/min, temperature 36.8°C (98.2°F), and respiratory rate 11/min. On physical examination, there is pitting edema of the upper and lower extremities bilaterally. An oropharyngeal examination is normal. Urinalysis shows the following results:
pH 6.2
Color dark brown
Red blood cell (RBC) count 18–20/HPF
White blood cell (WBC) count 3–4/HPF
Protein 1+
Cast RBC casts
Glucose absent
Crystal none
Ketone absent
Nitrite absent
24 h urine protein excretion 0.6 g
HPF: high-power field
Which of the following would best describe the light microscopy findings in this case?
A. Segmental sclerosis and hyalinosis
B. Wire looping of capillaries
C. Mesangial proliferation
D. Hypercellular and enlarged glomeruli (Correct Answer)
E. Crescentic proliferation consisting of glomerular parietal cells, macrophage, and fibrin
Explanation: ***Hypercellular and enlarged glomeruli***
- The patient's presentation with **cola-colored urine**, facial puffiness, edema, hypertension, and a recent history of sore throat points to **post-streptococcal glomerulonephritis (PSGN)**.
- Light microscopy in PSGN typically reveals **diffuse hypercellularity** due to proliferation of mesangial and endothelial cells, and infiltration by inflammatory cells, leading to enlarged glomeruli.
*Segmental sclerosis and hyalinosis*
- This finding is characteristic of **focal segmental glomerulosclerosis (FSGS)**, which typically presents with **nephrotic syndrome** (heavy proteinuria, hypoalbuminemia, severe edema).
- While there is proteinuria in this case, it is not in the nephrotic range, and other clinical features do not support FSGS.
*Wire looping of capillaries*
- **Wire looping** is a classic feature of **diffuse proliferative glomerulonephritis (DPGN)**, often seen in **lupus nephritis (Class III or IV)**.
- The patient’s clinical picture, particularly the antecedent sore throat and acute presentation, is not consistent with lupus nephritis.
*Mesangial proliferation*
- While mesangial proliferation occurs in PSGN, it is usually accompanied by **endocapillary proliferation** and inflammatory cell infiltration, making the glomeruli appear diffusely hypercellular and enlarged.
- Isolated mesangial proliferation is more characteristic of **IgA nephropathy**, which typically presents with recurrent episodes of gross hematuria, sometimes concurrent with or shortly after an upper respiratory infection.
*Crescentic proliferation consisting of glomerular parietal cells, macrophage, and fibrin*
- **Crescents** are pathognomonic of **rapidly progressive glomerulonephritis (RPGN)**, which involves severe and rapid loss of renal function.
- While PSGN can occasionally progress to RPGN, the typical presentation of PSGN usually does not involve prominent crescent formation unless severe.
Question 89: A 7-year-old girl is brought to the physician with complaints of erythema and rashes over the bridge of her nose and on her forehead for the past 6 months. She also has vesiculobullous and erythematous scaly crusted lesions on the scalp and around the perioral areas. Her parents report a history of worsening symptoms during exposure to sunlight, along with a history of joint pain and oral ulcers. Her temperature is 38.6°C (101.4°F), pulse is 88/min, and respirations are 20/min. On physical examination, pallor and cervical lymphadenopathy are present. On cutaneous examination, diffuse hair loss and hyperpigmented scaly lesions are present. Her laboratory studies show:
Hemoglobin 7.9 mg/dL
Total leukocyte count 6,300/mm3
Platelet count 167,000/mm3
Erythrocyte sedimentation rate 30 mm/h
ANA titer 1:520 (positive)
Which of the following most likely explains the mechanism of this condition?
A. Type II hypersensitivity
B. Type IV hypersensitivity
C. Type V hypersensitivity
D. Type I hypersensitivity
E. Type III hypersensitivity (Correct Answer)
Explanation: ***Type III hypersensitivity***
- This condition describes **Systemic Lupus Erythematosus (SLE)**, characterized by the formation of **immune complexes** that deposit in various tissues and trigger inflammation.
- The positive **ANA titer**, along with clinical features like **malar rash**, photosensitivity, arthritis, oral ulcers, and hematologic abnormalities (anemia, lymphadenopathy), are all consistent with SLE, which is a classic example of **Type III hypersensitivity**.
*Type II hypersensitivity*
- Involves **antibodies directly attacking antigens on cell surfaces**, leading to cell lysis or dysfunction.
- While SLE can have Type II features (e.g., hemolytic anemia), the broad systemic inflammation and diverse organ involvement are primarily driven by immune complex deposition.
*Type IV hypersensitivity*
- This is a **delayed-type hypersensitivity** reaction mediated by **T cells** and macrophages, not antibodies.
- Examples include contact dermatitis and tuberculin skin tests, which do not align with the multi-organ, immune complex-mediated pathology seen here.
*Type V hypersensitivity*
- A rare subtype of Type II hypersensitivity where antibodies **stimulate or inhibit cell function** by binding to cell surface receptors (e.g., Grave's disease, Myasthenia Gravis).
- It does not explain the widespread immune complex deposition and systemic inflammation characteristic of SLE.
*Type I hypersensitivity*
- Involves **IgE antibodies** binding to mast cells, leading to immediate release of histamine and other mediators upon antigen exposure.
- This type causes allergic reactions like hay fever or anaphylaxis and does not explain the chronic autoimmune manifestations of SLE.
Question 90: Physical exam of a 15-year-old female reveals impetigo around her mouth. A sample of the pus is taken and cultured. Growth reveals gram-positive cocci in chains that are bacitracin sensitive. Which of the following symptoms would be concerning for a serious sequela of this skin infection?
A. Myocarditis
B. Joint swelling
C. Fever
D. Chorea
E. Hematuria (Correct Answer)
Explanation: ***Hematuria***
- The description of **impetigo** around the mouth caused by **gram-positive cocci in chains** that are **bacitracin-sensitive** points to *Streptococcus pyogenes* (Group A Streptococcus).
- A serious sequela of streptococcal skin infections (impetigo) is **post-streptococcal glomerulonephritis (PSGN)**, which presents with **hematuria**, proteinuria, edema, and hypertension.
*Myocarditis*
- **Myocarditis** can be a complication of **acute rheumatic fever (ARF)**, which is a sequela of **streptococcal pharyngitis**, not typically streptococcal skin infections (impetigo).
- While both rheumatic fever and PSGN are caused by *Streptococcus pyogenes*, the specific **M-types** associated with skin infections differ from those causing pharyngitis and ARF.
*Joint swelling*
- **Arthritis** (joint swelling) is a major criterion for **acute rheumatic fever**, which follows **streptococcal pharyngitis**, not impetigo.
- Although PSGN can cause arthralgia, significant arthritis is not a primary or alarming symptom of PSGN.
*Fever*
- **Fever** is a general symptom that can accompany any infection, including impetigo itself or many other conditions.
- While fever can be present in PSGN, it is not a specific or unique indicator of this particular serious sequela.
*Chorea*
- **Sydenham's chorea** is a neurological manifestation of **acute rheumatic fever**, which develops after **streptococcal pharyngitis**, not impetigo.
- It presents as involuntary, purposeless movements and is not associated with PSGN following impetigo.
