Chronic Kidney Disease USMLE Step 1 Practice Question
A 64-year-old man with a 10-year history of multiple myeloma presents with progressive lower extremity edema. Vital signs show BP 142/88, HR 88, RR 16, Temp 37.2°C. Urinalysis reveals massive proteinuria (8.5 g/24 hours) without hematuria. Serum creatinine is 2.1 mg/dL. Kidney biopsy demonstrates amorphous eosinophilic deposits displaying apple-green birefringence under polarized light after Congo red staining. Which of the following best explains these renal findings?
Answer choices
- ASubepithelial immune complex deposition due to anti PLA2R antibodies
- BExtracellular deposition of misfolded proteins in beta pleated sheetsCorrect answer
- CLinear deposition of immunoglobulin along the basement membrane
- DLoss of negative charge in the glomerular basement membrane due to cytokines
- EMutation of a slit diaphragm structural protein
- FIntramembranous electron-dense deposits composed of IgG and complement complexes
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