Glomerular Diseases USMLE Step 1 Practice Question
A 51-year-old woman presents to the nephrology clinic with progressive lower extremity edema and foamy urine for 3 months. She was found to have a new IgG-kappa monoclonal spike on serum protein electrophoresis during workup for nephrotic syndrome. Physical examination reveals 3+ bilateral ankle edema and BP 158/92 mmHg. Laboratory studies show serum creatinine 2.8 mg/dL (baseline 0.9 mg/dL), albumin 2.1 g/dL, and 24-hour urine protein 8.5 g. Urinalysis demonstrates proteinuria without hematuria, casts, or dysmorphic RBCs. Kidney biopsy light microscopy shows nodular glomerulosclerosis with expansion of the glomerular basement membrane zone. Congo red staining of the biopsy specimen shows deposits with apple-green birefringence under polarized light microscopy. Which of the following is the most likely diagnosis?
Answer choices
- AMonoclonal immunoglobulin deposition disease (MIDD) with predominant κ light chain deposits
- BDiabetic nephropathy with concurrent monoclonal gammopathy of undetermined significance (MGUS)
- CAL amyloidosis secondary to monoclonal IgG productionCorrect answer
- DLight chain proximal tubulopathy with secondary glomerular involvement
- EMembranous nephropathy triggered by monoclonal protein deposition
- FMyeloma cast nephropathy with glomerular adaptation
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