Abstract: FR-PO0765
Severe Crescentic PR3-ANCA Glomerulonephritis with Prominent IgG4+ Plasma Cells: Diagnostic and Therapeutic Implications
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
- Imam, Nimrah H., Olive View UCLA Medical Center, Sylmar, California, United States
- Kamarzarian, Anita, Olive View UCLA Medical Center, Sylmar, California, United States
- Dagstanyan, Vardan, San Ysidro Health, San Ysidro, California, United States
- Jafari, Golriz, Olive View UCLA Medical Center, Sylmar, California, United States
- Pham, Phuong-Chi T., Olive View UCLA Medical Center, Sylmar, California, United States
- Hou, Jean, Cedars-Sinai Medical Center, Los Angeles, California, United States
Introduction
ANCA associated vasculitis (AAV) commonly presents with rapidly progressive glomerulonephritis (RPGN). Management of severe renal involvement remains nuanced. Additionally, increased IgG4+ plasma cells have been described in AAV, correlation with serum IgG4 levels and examination for possible systemic manifestations of IgG4 related disease should be done.
Case Description
A 62-year-old woman presented with AKI, creatinine of 3.38 mg/dL (baseline 0.6 mg/dL). Urinalysis showed microscopic hematuria (11–25 RBCs/HPF) and UPCR 0.46 g/g. Serologies revealed PR3-ANCA 67.5, with negative MPO-ANCA and anti-GBM.
Kidney biopsy demonstrated diffuse necrotizing crescentic glomerulonephritis (~80% crescents) with necrotizing arteritis, arteriolitis, and medullary angiitis. There was severe tubulointerstitial inflammation with granulomatous features, no proliferative features. Focally increased IgG4+ plasma cells were identified; however, there was no storiform fibrosis or obliterative phlebitis.
The findings were consistent with PR3-ANCA vasculitis with secondary IgG4+ plasma cell infiltration rather than IgG4 related disease. Patient did not have dense lymphoplasmacytic infiltrate or compatible clinical context. She was treated with cyclophosphamide and steroids. Serum IgG4 testing was requested for evaluation but did not follow up with testing.
Discussion
IgG4+ plasma cells may be observed in AAV and should not be misinterpreted as IgG4-RD without characteristic histopathologic features. In severe renal AAV with markedly reduced eGFR and extensive crescent formation, current KDIGO guidance supports cyclophosphamide based induction, given limited data for rituximab in severe cases of crescentic glomerulonephritis.
This case highlights a diagnostic pitfall of IgG4 staining in AAV and supports guideline directed use of cyclophosphamide in severe crescentic disease. Early recognition and appropriate immunosuppression are critical to improving renal outcomes.
Plasma cell rich interstitial linflammation, hematoxylin and eosin stain, magnification 400X. Increased IgG4 positive plasma cells noted by immunohistochemistry, magnification 400X.