Abstract: FR-PO0476
Extreme Free Light-Chain Elevation Without Cast Nephropathy in Multiple Myeloma
Session Information
- AKI: Case Reports - TMA, Vasculitis, Immune-Mediated Injury, and Systemic Disease
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 102 AKI: Clinical, Outcomes, and Trials
Authors
- Gharbieh, Yasmine, Sam Houston State University College of Osteopathic Medicine, Conroe, Texas, United States
- Lal, Yasir, Texoma Medical Center Inc, Denison, Texas, United States
Introduction
Renal impairment occurs in up to 50% of patients with multiple myeloma (MM) and significantly worsens prognosis. Light-chain cast nephropathy is the most common cause of acute kidney injury (AKI) and is typically associated with markedly elevated serum free light chains (FLCs). However, alternative mechanisms of renal injury may occur even with profound FLC elevation.
Case Description
A 68 year old woman with atrial fibrillation, HFpEF, hypertension, and type 2 diabetes presented with severe AKI, hypercalcemia, nephrotic-range proteinuria, and anemia. Labs showed creatinine 6.1 mg/dL, hemoglobin 9.5 g/dL, and serum free κ light chains >31,000 mg/L. Serum protein electrophoresis revealed a monoclonal spike and skeletal survey showed diffuse lytic lesions. Bone marrow biopsy demonstrated κ-restricted plasma cell myeloma involving 70% of marrow with 5% circulating plasma cells.
Empiric plasmapheresis and hemodialysis were initiated. However, kidney biopsy revealed acute tubular injury with calcium phosphate deposition and severe arteriosclerosis without evidence of cast nephropathy, monoclonal immunoglobulin deposition disease, or amyloidosis. Plasmapheresis was discontinued and the patient was treated with dexamethasone followed by CyBorD therapy.
Discussion
Cast nephropathy is the most common cause of acute kidney injury in MM and is strongly associated with serum FLC levels >500–1000 mg/L. However, markedly elevated FLC levels do not reliably predict cast formation. In this case, despite extreme FLC elevation, kidney biopsy demonstrated acute tubular injury with calcium phosphate deposition, consistent with hypercalcemia-associated injury rather than cast nephropathy. This underscores the heterogeneity of renal pathology in MM-associated AKI and the essential role of biopsy in guiding management, as reliance on FLC levels may lead to unnecessary interventions and delay appropriate therapy.
Calvaria demonstrating lytic lesions.