Glomerular Diseases USMLE Step 1 Practice Question
A 3-year-old boy presents with periorbital and pedal edema. Vital signs show BP 95/60 mmHg, HR 102/min, RR 22/min, temperature 37.2°C, and SpO2 98% on room air. Urinalysis demonstrates heavy proteinuria (4+ protein, 24-hour urine protein 3.5 g/day) consisting predominantly of albumin with no hematuria. Serum albumin is 1.8 g/dL. Kidney biopsy shows normal light microscopy findings. Which mechanism best explains the selective protein loss in this disorder?
Answer choices
- ALinear antibody deposition along type IV collagen
- BLoss of the negative charge barrier in the glomerular basement membraneCorrect answer
- CMesangial trapping of IgA-containing immune complexes
- DSubendothelial immune complex deposition with complement activation
- EAmyloid infiltration of the interstitium
- FCongenital nephrin mutation (NPHS1)
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