Abstract: FR-PO0767
Methimazole-Induced ANCA-Associated Vasculitis (AAV): Lessons from Two Cases
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
- Ojaimi, Nadim, University of Maryland Medical Center, Baltimore, Maryland, United States
- Patel, Ami Mahendrakumar, University of Maryland Medical Center, Baltimore, Maryland, United States
Introduction
Antithyroid drug–induced ANCA-associated vasculitis is a rare complication that may mimic infection or primary AAV. We report two methimazole-associated cases.
Case Description
Case 1: A 50-year-old woman recently off methimazole developed cough, pulmonary nodules, active urine sediment, and AKI. PR3-ANCA was positive; infectious work-up including bronchospcopy, MTB DNA, viral respiratory panel, and HIV were negative. Biopsy demonstrated necrotizing crescentic GN involving 50% of glomeruli.
Case 2: A 50-year-old man on methimazole developed DAH, respiratory failure, and dialysis-requiring AKI. p-ANCA/MPO were positive; other serologies were negative. Biopsy showed pauci-immune GN with arteritis. He improved after withdrawal and immunosuppression, stopping dialysis.
Discussion
Methimazole-induced AAV can range from renal-limited disease to severe pulmonary-renal syndrome with DAH and dialysis-requiring AKI. Although MPO-ANCA is typical, PR3 positivity may occur. Biopsy, methimazole withdrawal, and prompt immunosuppression are key.
Acknowledgment
Dr Autumn Larocque-Pathology.
Serologies and features
| Case # | Case 1 | Case 2 |
| ANCA Profile | PR3-ANCA positive,PR3 4.3; MPO negative | p-ANCA 1:320; MPO positive165; PR3 negative |
| Renal Involvement | Active urinary sediment; Cr peak 2.24 mg/dL | AKI requiring CRRT/iHD; Cr peak 11 mg/dL |
| Urine studies | Active sediment: >20 RBCs/hpf, 11–20 WBCs/hpf; UPCR 0.7–1 g/g; UACR 376 mg/g. | UA w 6-10 rbcs/hpf; UPCR 0.7 g/g |
| Pulmonary involvement | Bilateral pulmonary nodules and chronic upper respiratory symptoms concerning for pulmonary-renal involvement | Diffuse alveolar hemorrhage with hypoxemic respiratory failure |
| Biopsy findings | Necrotizing and crescentic GN involving 50% of glomeruli; mild IFTA ~20% | Severe pauci-immune ANCA vasculitis with fibrinoid necrosis, crescents, necrotizing arteritis, and mild to focally moderate IFTA |
Figure 1. Case 1 urine microscopy and kidney biopsy. Urine microscopy shows an RBC cast, upper left. H&E section shows an RBC cast, lower left, 60×. Jones stain shows a segmental necrotizing lesion, right, 40×.
Figure 2. Case 2 kidney biopsy. Left: vessel with fibrinoid necrosis, arrowhead, H&E, 20×. Right: glomerular crescent, arrowhead, with fibrinoid necrosis, arrow, PAMS, 20×.