Supplementary Material for: Fibrillary Glomerulonephritis and Multiple Myeloma, A Case Report and Literature Review

Introduction: Fibrillary glomerulonephritis (FGN) is a rare form of immune complex-mediated primary glomerular disease frequently coexisting with malignancies or autoimmune diseases. The kidney prognosis is extremely poor, with approximately 50% of patients progressing to end-stage kidney disease within two to four years after diagnosis. However, no established treatment currently exists. Case Presentation: Here we describe a rare case of FGN diagnosed in a patient progressing from monoclonal gammopathy to multiple myeloma. The histopathological findings of the kidney biopsy were consistent with classical FGN and revealed no evidence of myeloma cast nephropathy. Albumin-dominant, Bence Jones protein-negative proteinuria further supported this diagnosis. The patient was successfully treated with anti-myeloma chemotherapies including autologous stem cell transplant, resulting in significant improvement in kidney function. Conclusion: Based on our experience, secondary FGN associated with plasma cell neoplasms may represent a rare entity that responds favorably to anti-myeloma therapies. Initial investigations to rule out coexistent plasma cell neoplasms are crucial for the optimal management of FGN patients.