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Abstract: SA-PO207

Membranous Nephropathy Masquerading as Amyloid Nephropathy in a Multiple Myeloma Patient

Session Information

Category: Onconephrology

  • 1700 Onconephrology


  • Shiver, Lachlan P., University of South Florida, Tampa, Florida, United States
  • Cobb, Jessica K., University of South Florida, Tampa, Florida, United States
  • Russell, Charles, University of South Florida, Tampa, Florida, United States
  • Bassil, Claude, University of South Florida, Tampa, Florida, United States

Renal dysfunction is a common presentation in many plasma cell dyscrasias, including multiple myeloma. In these disorders, malignant plasma cells proliferate and produce monoclonal immunoglobulins (Ig). These Igs can result in myeloma cast nephropathy, light chain deposition disease, and most commonly, amyloid light chain (AL) amyloidosis. In AL amyloidosis, Ig light chains deposit into renal parenchymal tissue and cause proteinuria and progressive chronic renal failure. Therefore, dysproteinemia-associated kidney disease should be suspected in any patient with plasma cell dyscrasia and renal dysfunction.

Case Description

The patient was a 73-year-old Caucasian female first diagnosed with multiple myeloma, Durie-Salmon Stage IIIA, in 2014. She underwent chemotherapy and autologous stem cell transplant (SCT) in 2015, with complete remission. After SCT, she continued on maintenance immunomodulatory agents with a good hematological response. In 2022 she developed progressive lower extremity edema, worsening pain, and increased fatigue. Workup revealed proteinuria of 7g/24hr and increased urinary M-spikes. Given clinical suspicion for dysproteinemia- associated kidney disease, the patient underwent a repeat bone marrow and kidney biopsy.

The bone marrow biopsy revealed myeloma plasma cells occupying only 5% of marrow. Kidney biopsy revealed immune complex deposits involving capillary loops in a subepithelial distribution, a finding consistent with membranous nephropathy (MN). Notably, Congo red staining was negative and ruled out amyloid deposits. Anti-phospholipase A2 Receptor (PLA-2R) immunostaining was negative, and nerve epidermal growth factor-like 1 (NELL-1) immunostaining was positive. Age-based cancer screening was initiated, and NSAIDS were discontinued.


Herein, we present a case of NELL-1 positive MN in a patient with multiple myeloma. Membranous nephropathy is the second leading cause of nephrotic syndrome. MN can be idiopathic, related to infection, medication use (NSAIDs), or autoimmune diseases. Notably, NELL-1-positive MN has been linked to solid organ malignancies. Management of these patients should emphasize discontinuing possible causative agents and a thorough cancer screening. This case represents the importance of a thorough workup of nephrotic syndrome, even in patients with a high pretest probability of AL amyloidosis.