Abstract: SA-PO0704
PR3-ANCA Positivity Without Vasculitis: IgM-Dominant Immune Complex Glomerulonephritis Revealing Subacute Bartonella Endocarditis
Session Information
- Glomerular Diseases: Complement-Mediated Glomerulopathies and Infection-Related GN
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
- Panhwar, Muhammad Yaseen, University of Rochester Medical Center, Rochester, New York, United States
- Alom, Md Saiful, University of Rochester Medical Center, Rochester, New York, United States
- Lusco, Mark, University of Rochester Medical Center, Rochester, New York, United States
Introduction
Infective endocarditis-associated glomerulonephritis (IE-GN) may mimic ANCA-associated vasculitis (AAV), often with PR3-ANCA positivity and crescentic or necrotizing lesions. However, PR3-ANCA positivity with IgM-dominant immune complex deposition in the absence of vasculitis is uncommon and presents a diagnostic challenge.
Case Description
A 57-year-old man with a bioprosthetic aortic valve presented with 2 months of fatigue, 55-lb weight loss, hematuria, and AKI (Cr 2.9 mg/dL from baseline 1.1). Serologies revealed PR3-ANCA positivity, hypocomplementemia (low C3/C4), and elevated rheumatoid factor. Initial kidney biopsy showed IgA-predominant immune complex GN without crescents, and high-dose corticosteroids were initiated. He was readmitted 2 weeks later with rapidly progressive kidney failure (Cr >9 mg/dL), hemoptysis, thrombocytopenia, and dialysis was initiated. Repeat biopsy showed IgM-dominant (2–3+) mesangial and segmental capillary loop deposits with strong C3 and C1q staining, diffuse ATN with numerous RBC casts, and no necrosis, crescents, or vasculitis. Findings indicated infection-related immune complex glomerulonephritis and warfarin-associated nephropathy. Bronchoscopy confirmed diffuse alveolar hemorrhage. TEE showed severe prosthetic valve thickening and dysfunction without clear vegetation. Bartonella henselae IgG returned positive, and blood cultures were negative. Overall, consistent with culture-negative Bartonella endocarditis. Immunosuppression was discontinued. Despite targeted antimicrobial therapy and renal replacement therapy, his course was complicated by biventricular failure and refractory shock, and he died despite maximal care.
Discussion
IE-associated GN frequently shows immune complex deposition and may be PR3-ANCA positive. Many reported cases histologically resemble AAV with crescentic or pauci-immune patterns. This case is unusual due to: PR3-ANCA positivity, IgM-dominant full-house immune complex pattern, Absence of necrotizing or crescentic vasculitis.
This discordance highlights that ANCA positivity alone does not always establish primary AAV and may represent an infection-driven autoimmune process. Hypocomplementemia, rheumatoid factor elevation, splenomegaly, & prosthetic valve dysfunction were critical clues favoring infection-related GN. Repeat biopsy was essential in redirecting management away from immunosuppression.