A 70-year-old man has lytic bone lesions, serum M-protein of 4 g/dL, and bone marrow showing 30% plasma cells. He develops acute kidney injury. The most important mechanism of renal injury in multiple myeloma is:

• A Immunotactoid glomerulopathy from whole IgG deposition
• B Membranoproliferative GN from complement activation
• C Interstitial nephritis from plasma cell infiltration
• D Cast nephropathy from light chain precipitation in tubules ✓

Explanation

Myeloma kidney (cast nephropathy) is the most common renal lesion in multiple myeloma. Excess free light chains (Bence Jones proteins) are filtered and precipitate in distal tubules, forming casts with Tamm-Horsfall protein that obstruct and injure tubular epithelium. AL amyloidosis and light chain deposition disease are additional mechanisms but cast nephropathy predominates.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.