Abstract: FR-PO0480
Lambda Light Chain-Mediated AKI from a Mediastinal Plasmacytoma with Minimal Bone Marrow Involvement
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
- Elliott, Andrew S., University of Kentucky College of Medicine, Lexington, Kentucky, United States
- Webb, Jon, University of Kentucky College of Medicine, Lexington, Kentucky, United States
- Younis, Mohamed Ahmed, University of Kentucky College of Medicine, Lexington, Kentucky, United States
Group or Team Name
- University of Kentucky College of Medicine Division of Nephrology
Introduction
Acute kidney injury (AKI) complicates multiple myeloma in 20–50% of cases, commonly due to light chain cast nephropathy. Cast nephropathy often occurs in the setting of high tumor burden with diffuse marrow involvement, leading to serum free light chain levels >150mg/dL. Only 20% of myeloma-associated plasmacytomas are extramedullary and mediastinal plasmacytomas are extremely rare. We report a case of oliguric AKI due to λ light chain overproduction from a posterior mediastinal plasmacytoma with only 0.5–1% bone marrow involvement.
Case Description
An 87-year-old woman presented with oliguric AKI and serum creatinine of 7.52 mg/dL. Serum protein analysis showed highly elevated λ light chain with a severely abnormal κ/λ ratio. A posterior mediastinal mass seen on chest computerized tomography led to a biopsy showing a λ chain-restricted plasmacytoma. A bone marrow biopsy revealed 0.5-1% λ-restricted aberrant plasma cells and a peripheral blood smear showed no circulating plasma cells. The AKI was determined to be associated with the mediastinal plasmacytoma given the low marrow involvement. Aggressive intravenous hydration and cyclophosphamide, bortezomib, dexamethasone therapy was initiated. Serum creatinine improved from 7.52 to 1.55 mg/dL over 6 days, indicating rapid renal recovery with early reduction in light chains.
Discussion
This case exemplifies that extramedullary plasmacytomas, without prominent marrow disease, can produce enough monoclonal light chains to cause severe cast nephropathy and AKI. The mediastinal location is especially rare, accounting for a tiny fraction of extramedullary plasmacytomas. The striking renal recovery following chemotherapy and hydration is consistent with evidence that a rapid reduction in light chains in the first weeks of therapy predicts renal response. This case highlights the importance of complete imaging and tissue biopsy in patients with light chain-mediated AKI and low marrow involvement, as the source of nephrotoxic light chains may be an occult extramedullary plasmacytoma.