Abstract: FR-PO0708
Membranous-Like Glomerulopathy with Masked IgG-k Deposits in a Pediatric Patient with Juvenile Idiopathic Arthritis (JIA)
Session Information
- Pediatric Nephrology: CKD, ESKD, and Glomerular Diseases
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pediatric Nephrology
- 1900 Pediatric Nephrology
Authors
- Chati, Priyanka, Ann and Robert H Lurie Children's Hospital of Chicago Foundation, Chicago, Illinois, United States
- Krissberg, Jill, Ann and Robert H Lurie Children's Hospital of Chicago Foundation, Chicago, Illinois, United States
- Henriksen, Kammi J., The University of Chicago, Chicago, Illinois, United States
- Nolan, Brian, Ann and Robert H Lurie Children's Hospital of Chicago Foundation, Chicago, Illinois, United States
- Harris, Meredith, Ann and Robert H Lurie Children's Hospital of Chicago Foundation, Chicago, Illinois, United States
Introduction
Membranous-like glomerulopathy with masked IgG-kappa deposits (MGMID) is a rare, biopsy-diagnosed condition seen predominantly in young females. It presents with proteinuria, microscopic hematuria, and negative immune serologies. Routine immunofluorescence (IF) often shows only C3 staining, leading to misdiagnoses such as C3 glomerulonephritis (C3GN). Diagnosis requires repeat IF on paraffin-embedded tissue with protease digestion to "unmask" the IgG-kappa deposits.
Case Description
We report a case of a 12-year-old Hispanic female with systemic JIA complicated by hypertension and posterior reversible encephalopathy syndrome and acute anterior uveitis, on biweekly tocilizumab, referred to nephrology for persistent proteinuria (UPC 1–1.5 g/g) without hematuria. Her kidney function was normal. Serologic workup was unrevealing except for positive ANA at 640 and mildly low C3 of 73mg/dL.
Initial kidney biopsy revealed features concerning for mild C3GN vs latent infection-related GN. C3GN panel was negative. Lisinopril was initiated for 2 months, but UPC worsened to 2.2 g/g. High dose prednisone (60mg daily-1mg/kg) was initiated for 4 weeks and resulted in mild improvement with UPC 1.4 g/g. Steroids were tapered, and she initiated Mycophenolate mofetil (MMF) (600mg/m2) twice daily. Tocilizumab was spaced to every 6 weeks after MMF initiation.
Despite immunosuppression, proteinuria persisted (UPC 1.75 g/g), prompting repeat biopsy. Findings included glomerular basement membrane thickening with spikes, mesangial hypercellularity, and segmental sclerosis. Routine IF again showed isolated C3 staining. Based on her autoimmune history, repeat IF on protease-digested paraffin tissue confirmed IgG-kappa deposits, consistent with MGMID.
She remains on MMF and lisinopril with UPC improving to 0.46 g/g at 6 months. Kidney function remains normal, and tocilizumab was discontinued due to JIA remission.
Discussion
MGMID often mimics C3GN due to dominant C3 staining, leading to misclassification. Outcomes vary from spontaneous remission or mild disease to end stage renal disease. Optimal treatment remains unclear as some patients respond to RAAS blockade alone while some require immunosuppression. While linked to other autoimmune diseases, MGMID is rarely reported with autoinflammatory conditions like systemic JIA.