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Abstract: PO1892

Membranous-Like Glomerulopathy with Masked Monoclonal IgG Deposits

Session Information

Category: Onco-Nephrology

  • 1500 Onco-Nephrology

Authors

  • Merchant, Kumail, Steven and Alexandra Cohen Children's Medical Center, New Hyde Park, New York, United States
  • Sethna, Christine B., Steven and Alexandra Cohen Children's Medical Center, New Hyde Park, New York, United States
  • Sachdeva, Mala, Northwell Health, New Hyde Park, New York, United States
  • Bijol, Vanesa, Northwell Health, New Hyde Park, New York, United States
  • Jhaveri, Kenar D., Northwell Health, New Hyde Park, New York, United States
Introduction

Membranous-like glomerulopathy with masked monoclonal IgG deposits (MGMID) is a recently described entity characterized by a membranous pattern of injury with monoclonal IgG-kappa restriction, unmasked by pronase digestion on formalin-fixed paraffin-embedded (FFPE) tissue by immunofluorescence microscopy (IF). Retrospective pathology and chart review was performed within a large health system in the USA between 2019-2021 identifying 5 patients.

Case Description

All 5 patients were Caucasian females with median age 17 years (range 12-48). On presentation, 4 patients had elevated urine protein to creatinine ratio (UPC), 3 had microscopic hematuria, and 1 patient had an eGFR <90ml/min/1.73m2. Of note, 1 patient presented post-partum. Serologic workup revealed positive antinuclear antibody (ANA) in 1 patient (see table) who had a known history of juvenile idiopathic arthritis. Kidney biopsy revealed a membranous pattern of glomerular injury in all patients, with global glomerulosclerosis from 0-31%, segmental glomerulosclerosis from 2-7%, and interstitial fibrosis and tubular atrophy from 2-50%. Electron microscopy revealed subepithelial/intramembranous deposits without substructural organization. Finely granular capillary wall reactivity for C3 was noted on routine IF on frozen sections. On FFPE after pronase digestion, all cases revealed glomerular capillary wall staining for gamma-1 (4 cases) or gamma-3 (1 case) and kappa light chains; lambda light chains were negative. Extensive hematologic workup was negative for monoclonal bands or lymphoproliferative processes. All patients were treated with angiotensin converting enzyme inhibitor (ACEi) or angiotensin receptor blocker (ARB) therapy, and 2 patients were also treated with Rituximab. Four patients had an improvement in UPC. None of the patients required kidney replacement therapy.

Discussion

MGMID is a peculiar entity with monoclonal IgG glomerular deposits primarily affecting young Caucasian females, without obvious correlation to monoclonal lymphoproliferative disorder. Treatment with ACEi or ARB +/- Rituximab improved UPC in most patients in this case series. Better understanding of this entity is important to guide therapy.