Histology USMLE Step 1 Practice Question
A 28-year-old man with recurrent urinary tract infections and hematuria presents with BP 128/82 mmHg, HR 92/min, and serum creatinine 1.4 mg/dL. Renal biopsy histology reveals a thin, discontinuous glomerular basement membrane. Electron microscopy demonstrates splitting of the lamina densa into two layers with characteristic 'basket-weave' appearance. Urine dipstick shows no proteinuria. Which genetic abnormality most likely explains these findings?
Answer choices
- AMutation in COL4A3 gene encoding type IV collagen alpha-3 chainCorrect answer
- BMutation in APOL1 gene affecting apolipoprotein L1
- CMutation in MYH9 gene encoding non-muscle myosin heavy chain
- DMutation in NPHS1 gene encoding nephrin
- EMutation in WT1 gene encoding Wilms tumor suppressor protein
- FMutation in LAMB2 gene encoding laminin beta-2 chain
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