Abstract: SA-PO0765
Masked IgG-κ Glomerulopathy with Striated Deposits Responding to Daratumumab: A Rare Monoclonal Gammopathy of Renal Significance Variant
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
- Cara, Anila, Mayo Clinic Minnesota, Rochester, Minnesota, United States
- Vargas-Brochero, Maria J., Mayo Clinic Minnesota, Rochester, Minnesota, United States
- Laxamana, Trisha D., Mayo Clinic Minnesota, Rochester, Minnesota, United States
- Zhang, Pingchuan, Mayo Clinic Minnesota, Rochester, Minnesota, United States
- Sethi, Sanjeev, Mayo Clinic Minnesota, Rochester, Minnesota, United States
- Fervenza, Fernando C., Mayo Clinic Minnesota, Rochester, Minnesota, United States
Introduction
Monoclonal gammopathy of renal significance (MGRS) comprises a spectrum of kidney diseases caused by nephrotoxic monoclonal immunoglobulins produced by B-cell or plasma cell clone that does not meet criteria for overt hematologic malignancy. Rarely, glomerular deposits exhibit atypical ultrastructural organization, which may complicate classification.
Case Description
A 65-year-old woman with a history of MGUS presented with nephrotic syndrome (urine protein-to-creatinine ratio 6.9 g/g), serum albumin (3.2 g/dL), hematuria and preserved kidney function (eGFR 82 ml/min/1.72m2). Kidney biopsy demonstrated a membranoproliferative pattern with double contours and mild endocapillary hypercellularity. Routine immunofluorescence showed IgM-predominance without light chain restriction; however, paraffin immunofluorescence after antigen retrieval revealed masked IgG-κ–restricted deposits. Electron microscopy showed mesangial/focal subendothelial electron-dense deposits with a distinctive striated ultrastructure. Congo red and DNAJB9 staining were negative. Laser microdissection with liquid chromatography–tandem mass spectrometry did not identify peptides corresponding to known membranous nephropathy–associated antigens.
Bone marrow biopsy and PET-CT revealed no evidence of plasma cell neoplasm. The patient was treated with six cycles of daratumumab, bortezomib, and dexamethasone. At 6 months, proteinuria declined to 0.7 g/day, serum albumin normalized (3.7 g/dL), and eGFR remained stable at 83 ml/min/1.72m2.
Discussion
This case expands the spectrum of MGRS-associated glomerulopathies by highlighting masked monoclonal deposits with rare, striated ultrastructure. Recognition of this pattern is critical, as it may respond favorably to clone-directed therapy despite no detectable hematologic malignancy.