Abstract: SA-PO0180
Monoclonal Gammopathy of Numerous Renal Significance
Session Information
- Onconephrology: MGRS, HSCT, Electrolytes, RCC, and More
November 08, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Onconephrology
- 1700 Onconephrology
Authors
- Khor, Si Yuan, Brigham and Women's Hospital, Boston, Massachusetts, United States
- Shah, Sujal I., Brigham and Women's Hospital, Boston, Massachusetts, United States
- Chowdhury, Raad Bin Zakir, Brigham and Women's Hospital, Boston, Massachusetts, United States
Introduction
Monoclonal gammopathy of renal significance (MGRS) involves nephrotoxic monoclonal immunoglobulin production without meeting criteria for over B or plasma cell malignancies. Rarely, organized and non-organized forms coexist. We report a unique case with both patterns and concurrent membranous nephropathy (MN).
Case Description
51 y.o. male presented with edema, AKI and proteinuria. Workup notable for creatinine (sCr) 2.0 mg/dL from 1.2 mg/dL, urinalysis 3+ protein, UACR 2.5g/g, C3 51 mg/dL, C4 7 mg/dL, Protein electrophoresis showed IgM kappa, serum free light chains revealed Kappa 147 mg/L; Cryoglobulin 7%. Kidney biopsy showed MIDD, IgM/Kappa with extensive subendothelial deposits, pseudothrombi suggestive of type 1 cryoglobulinemia, and MN with subendothelial electron-dense deposits and negative PLA2R. He received pulse dose steroids with 3 sessions of plasmapheresis. MYD88 mutation, often seen with lymphoplasmacytic lymphoma (LPL) was detected. Bone marrow biopsy and flow cytometry were unrevealing. He was treated as LPL and received dexamethasone, rituximab and cyclophosphamide (DRC) x 6 cycles. He achieved excellent renal and hematological responses with resolution of edema, decreased UACR to 47mg/g, improved sCr to 1.2 mg/dL.
Discussion
This case reports overlapping pathologies. MIDD is characterized by deposition of kappa light chain, rarely a heavy chain or both. Cryoglobulinemia frequently manifests with organized microtubular immunoglobulin deposits, often driven by IgM. Our biopsy did not reveal substructures, but had pseudothrombi with serum cryoglobulins. Evidence for plasmapheresis is limited, but was pursued due to rapidly evolving renal failure and positive cryoglobulin level. Bone marrow biopsy did not reveal plasma cell or lymphoid neoplasm. Given the presence of IgM Kappa, cryoglobulin deposits in kidney and detectable MYD88 mutation, it was treated as LPL.