Features of Autoimmune Pancreatitis Associated With Inflammatory Bowel Diseases.

BACKGROUND & AIMS: Few people know of autoimmune pancreatitis (AIP), a rare disorder associated with inflammatory bowel diseases (IBD). We aimed to describe phenotype and outcomes of IBD and AIP when associated.

METHODS: We performed a retrospective study of cases of AIP in IBD identified from the multicenter Groupe d'Etude Thérapeutique des Affections Inflammatoires du tube Digestif in Belgium and France from July 2012 through July 2015. Patients were diagnosed with AIP based on the International Consensus Diagnostic Criteria for AIP. A definitive AIP diagnosis was based on histological analysis of pancreatic resection specimens or samples collected by fine-needle aspiration during endoscopic ultrasound. Patients with probable type 1 AIP were identified based on imaging findings, clinical and/or radiologic responses to steroids, level of serum immunoglobulin G4, and involvement of other organs. Patients with probable type 2 AIP were identified based on imaging findings, clinical and/or radiologic responses to steroids, and association with IBD. The primary objective was to collect information on the characteristics of AIP in patients with IBD. We also compared features of patients with IBD with and without AIP in a case-control analysis, using multivariate analysis.

RESULTS: We analyzed data from 91 individuals with AIP and IBD (47 women) seen at 23 centers (58 had ulcerative colitis [UC] and 33 Crohn's disease [CD]). Eighty-nine patients had type 2 AIP, and 2 patients had type 1 AIP. The mean age at diagnosis of AIP was 35 ± 12 years, and for IBD it was 32 ± 12 years. AIP preceded IBD in 19 patients (21%). Over a mean follow-up period of 5.7 ± 4.9 years, 31 patients (34%) relapsed, 11 patients (12%) developed diabetes, and 17 patients (19%) developed exocrine pancreatic insufficiency. In patients with UC, factors independently associated with AIP included proctitis (odds ratio [OR], 2.9; 95% confidence interval [CI], 1.3-6.3; P = .007) and colectomy (OR, 7.1; 95% CI, 2.5-20; P = .0003). In patients with CD, AIP was significantly associated with fewer perianal lesions (OR, 0.16; 95% CI, 0.03-0.77; P = .023), non-stricturing non-penetrating CD (OR, 6.7; 95% CI, 1.25-33.3; P = .0029), and higher rate of colectomy (OR, 27.8; 95% CI, 3.6-217; P = .0029).

CONCLUSIONS: In a multicenter retrospective analysis of patients with AIP and IBD, followed for an average of 5.7 ± 4.9 years, we found most to have type 2 AIP. Two-thirds of patients have UC, often with proctitis. One-third of patients have CD, often with inflammatory features. Patients with IBD and AIP have higher rates of colectomy than patients with just IBD.