Abstract: TH-PO0848
When the Treatment Becomes the Disease: Rituximab-Induced Crohn Disease in PR3+ ANCA-Associated Vasculitis
Session Information
- Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
October 22, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
- 1900 Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
Authors
- Amin, Bina, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Goldbeck, Lauren Diane, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Power, Sydney, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
- Jain, Koyal, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Introduction
Rituximab is an anti-CD20 monoclonal antibody commonly used for the treatment of antineutrophil cytoplasmic antibody (ANCA) vasculitis. There are many side effects to Rituximab, but inflammatory bowel disease (IBD) resulting from Rituximab use is uncommon. We present a rare case of IBD and need for early recognition.
Case Description
A 29-year-old woman with PR3-positive ANCA vasculitis with saddle nose deformity and subglottic stenosis presented with hematochezia. She received Rituximab every 6 months and mycophenolate for 4 years and achieved remission, thus mycophenolate was discontinued 1 month before admission. Over weeks, she developed arthralgias, fever, and bilateral shin nodules, and then hematochezia. CRP was elevated to 91 mg/L. Punch biopsy of nodules demonstrated granulomatous inflammation with fibrinoid vessel wall change, consistent with vasculitis. CT abdomen showed ileocecitis. Bidirectional endoscopy showed esophageal ulcerations, deep ulcerations in the ascending colon and cecum, and terminal ileal inflammation.
The differential included infection, vasculitis-associated enterocolitis, and IBD. Infectious workup was negative. ANCA titers were negative with suppressed CD19 B-cells. Endoscopic biopsies showed active ileitis and colitis with chronicity, esophageal and ileal granulomatous inflammation, and negative infectious stains altogether consistent with Crohn's disease (CD). She failed steroids and was treated with Upadacitinib 45 mg daily. Her hematochezia resolved and CRP normalized.
Discussion
This case illustrates an underrecognized complication of rituximab: de novo IBD. The chronic granulomatous ileocecal inflammation without vasculocentric changes, negative infectious workup, and negative ANCA titers with complete B-cell depletion pointed towards rituximab-induced CD. This is a rare but recognized complication thought to be related to rituximab-induced B-cell depletion, disrupting intestinal mucosal immune tolerance. Both ANCA vasculitis and CD can cause granulomatous inflammation in the gastrointestinal (GI) tract. A multidisciplinary approach and high degree of suspicion are needed to diagnose rituximab-associated IBD. New GI symptoms in patients on Rituximab should not be reflexively attributed to infection or vasculitis flare. De novo IBD deserves a spot on the differential, and early recognition can change the treatment trajectory entirely.