A 58-year-old man presents with back pain, anaemia (Hb 8.8 g/dL), and acute kidney injury (creatinine 6.2 mg/dL). Serum protein electrophoresis shows an M-spike. Urine shows no proteinuria by dipstick but urine immunofixation reveals monoclonal kappa light chains. Serum calcium is 11.8 mg/dL. Kidney biopsy shows eosinophilic intraluminal casts with fracture lines and multinucleated giant cells. Which is the MOST appropriate next step to improve renal outcome?

• A Initiate urgent haemodialysis
• B Perform plasma exchange daily for 5 sessions
• C Administer high-dose methylprednisolone alone
• D Start a bortezomib-based chemotherapy regimen ✓

Explanation

This is myeloma cast nephropathy (myeloma kidney). The key to renal recovery is rapid reduction of free light chains with bortezorib-based chemotherapy (e.g., cyclophosphamide-bortezomib-dexamethasone). Plasma exchange has not shown consistent benefit in randomized trials and is not standard first-line. Dialysis supports but does not remove light chains efficiently. High-dose steroid alone is insufficient to rapidly lower the nephrotoxic light chain load.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.