Abstract: FR-PO0790
Biopsy-Proven Myeloperoxidase (MPO)-ANCA Glomerulonephritis Relapse Despite Peripheral CD19+ B-Cell Depletion After Rituximab
Session Information
- Glomerular Diseases: ANCA Vasculitis, Anti-GBM Disease, and Crescentic GN
October 23, 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
- Salik, Ahmed, Corewell Health William Beaumont University Hospital, Royal Oak, Michigan, United States
- Garlapaty, Vamshi K., Corewell Health William Beaumont University Hospital, Royal Oak, Michigan, United States
- Abu-Khaled, Jamal, Corewell Health William Beaumont University Hospital, Royal Oak, Michigan, United States
- Zhang, Ping L., Corewell Health William Beaumont University Hospital, Royal Oak, Michigan, United States
Introduction
MPO-ANCA vasculitis frequently manifests as rapidly progressive glomerulonephritis leading to acute kidney injury. B-cell depletion with agents like rituximab has emerged as a cornerstone of both induction and maintenance therapy in ANCA-associated vasculitis. Kidney relapse of MPO-ANCA vasculitis despite undetectable peripheral CD19+ B cells after rituximab challenges reliance on peripheral B-cell monitoring alone.
Case Description
A 64-year-old woman with hypertension, type 2 diabetes, and seropositive rheumatoid arthritis had biopsy-proven MPO-ANCA pauci-immune crescentic glomerulonephritis with concurrent secondary membranous nephropathy diagnosed in September 2025. She was treated with pulse steroids, rituximab, and maintained on avacopan and low-dose steroids. She responded well, with creatinine improving from 1.8 to 1.1 mg/dL, MPO antibody decreasing from >134 to 7.5 U/ml, and UPCR improving from 1.26 to 0.9 g/g by January 2026. Prior to her scheduled maintenance rituximab in April 2026, labs showed acute kidney injury and active urine sediment: creatinine 3.12 mg/dL, UPCR 2.36 g/g, and UA with 21 RBCs/HPF. p-ANCA was >1:640, and MPO antibody titer had risen to 50 U/ml. Flow cytometry showed CD19 B-cells at 0%. Repeat kidney biopsy demonstrated relapse of ANCA-associated crescentic glomerulonephritis with focal fibrinoid necrosis and fibrocellular crescent formation, with persistent secondary membranous glomerulopathy and mild interstitial fibrosis and tubular atrophy. She was treated with pulse steroids, cyclophosphamide and was given her maintenance dose of rituximab.
Discussion
This case illustrates a clinicopathologic relapse despite peripheral B-cell depletion. Rising MPO titers and recurrent hematuria/proteinuria preceded biopsy-proven relapse of crescentic glomerulonephritis, while standard peripheral flow cytometry demonstrated complete CD19+ B-cell depletion. Relying solely on CD19 count does not reliably exclude ongoing pathogenic humoral immunity and should not be used in isolation to exclude active renal vasculitis. Possible mechanisms include persistent CD20-negative plasma cell–mediated ANCA production, incomplete depletion of tissue-resident B cells, and possible T cell–mediated mechanisms of injury. In patients with worsening kidney function and active urine sediment, repeat kidney biopsy remains essential even when peripheral CD19 B-cells are undetectable.