Which mechanism most directly explains renal failure in cast nephropathy of multiple myeloma?
- A Obstruction of distal tubules by complexes of free light chains with uromodulin ✓
- B Deposition of amyloid fibrils in glomeruli
- C Proliferative glomerulonephritis caused by immune complex deposition
- D Direct invasion of renal parenchyma by malignant plasma cells
Correct answer: A. Obstruction of distal tubules by complexes of free light chains with uromodulin
Explanation
Excessive monoclonal free light chains filtered at the glomerulus bind uromodulin (the Tamm-Horsfall protein) in the distal nephron, forming large obstructive casts surrounded by multinucleated giant cells, producing myeloma kidney. Renal failure is aggravated by dehydration, hypercalcaemia and contrast exposure. AL amyloidosis deposits amyloid in vessels and mesangium rather than forming tubular casts, and direct plasma cell infiltration of kidney parenchyma is rare and not the usual cause.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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