In multiple myeloma, renal failure most often results from which mechanism?
- A Immune complex deposition in glomerular capillary loops
- B Obstruction of distal tubules by casts of light chains complexed with Tamm-Horsfall protein ✓
- C Direct invasion of renal parenchyma by malignant plasma cells
- D Thrombotic microangiopathy triggered by free light chains
Correct answer: B. Obstruction of distal tubules by casts of light chains complexed with Tamm-Horsfall protein
Explanation
Free monoclonal light chains filtered by the glomerulus bind Tamm-Horsfall protein in the distal tubule, forming obstructive casts surrounded by multinucleated giant cells; this cast nephropathy, also called myeloma kidney, is the leading cause of renal failure in myeloma. Light chains can also cause AL amyloidosis with glomerular deposits, but immune-complex proliferative glomerulonephritis and thrombotic microangiopathy are not the dominant mechanisms.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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