Kidney Week

Abstract: SA-PO0757

Immunoglobulins Running Wild: A Rare Case of Proliferative Glomerulonephritis with Monoclonal Immunoglobulin Deposits (PGNMID) Secondary to Waldenstrom Macroglobulinemia

Session Information

• Glomerular Diseases: Lupus Nephritis, Monoclonal Gammopathy-Related Disease, and Transplantation
  October 24, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics

Authors

• Chhaya, Richa, Icahn School of Medicine at Mount Sinai, New York, New York, United States

Richa Chhaya, MD

• Stillman, Isaac Ely, Icahn School of Medicine at Mount Sinai, New York, New York, United States

Isaac Ely Stillman, MD

• Farouk, Samira S., Icahn School of Medicine at Mount Sinai, New York, New York, United States

Samira S. Farouk, MD, MS, FASN

• Deshpande, Priya, Icahn School of Medicine at Mount Sinai, New York, New York, United States

Priya Deshpande, MD

Introduction

PGNMID is a rare glomerular disease within the spectrum of monoclonal gammopathies of renal significance (MGRS). The most common kidney biopsy finding is monoclonal staining with IgG3 and kappa deposits. Here, we describe a rare case of biopsy proven PGNMID secondary to glomerular IgM deposition that presented with rapidly progressive acute kidney injury (AKI) and nephrotic range proteinuria in a patient with known Waldenstrom’s macroglobulinemia (WM).

Case Description

A 79-year-old male with untreated WM, diagnosed three months prior, presented to nephrology clinic for a routine visit. Laboratory studies showed a serum creatinine elevation to 2.2mg/dL from baseline 0.7mg/dL ten days prior. Urinalysis showed 26-50 RBC and 3.5g/g of proteinuria, new from baseline one month prior, prompting hospital admission. Serologic workup revealed low C3 at 31mg/dL, low C4 at <3mg/dL, elevated antinuclear antibody titer (ANA) at 1:320, total IgM level of 4,962mg/dL, free kappa level of 1,188mg/l, free kappa/lambda ratio of 56.3, and elevated serum viscosity level of 4.4 relative to saline. He received 500mg of IV Solumedrol for three days, after which he underwent a kidney biopsy showing a membranoproliferative pattern with IgM and kappa deposits, along with a positive Periodic Acid-Schiff (PAS) stain for pseudothrombi within the capillary loops. Immunofixation showed confluent 4+ glomerular staining for IgM and 3+ for kappa, confirming the diagnosis of PGNMID. He was treated with steroids, bendamustine and plasmapharesis with improvement in his AKI after 10 days to a nadir creatinine of 1.13mg/dL.

Discussion

Renal manifestations of WM are unusual. Common pathologies include AL amyloidosis, Cryoglobulinemic Glomerulonephritis and lymphoplasmacytic infiltration of the kidney. This case highlights PGNMID as a rare and heterogenous consequence of WM, with IgM being the pathogenic driver instead of the more commonly reported IgG. While there is limited data for treatment of PGNMID specifically, clone directed therapy is the gold standard for treatment of MGRS. Anti plasma-cell agents such as daratumumab and bortezomib, along with anti-CD20 agents such as rituximab have proven effective. PGNMID is a novel diagnosis, and more data is needed to understand its pathogenesis and to guide treatment.