Unraveling the relationship between autoimmune pancreatitis type 2 and inflammatory bowel disease: Results from two centers and systematic review of the literature.

INTRODUCTION: The relationship between autoimmune pancreatitis (AIP) type 2 and inflammatory bowel disease (IBD) has been established and previously described within International Consensus Diagnostic Criteria. However, it is unknown if the presence of IBD changes the natural disease course of AIP type 2. Our aim was to investigate the association between AIP type 2 and IBD as well as to systematically summarize all the existing evidence in the literature. METHODS: Electronic medical record analysis was conducted in two centers (in Stockholm, Sweden, and Milan, Italy; records dated between January 2001 and June 2021). Additionally, we conducted a systematic review of the literature. RESULTS: A total of 35 patients (18 females, 51.4%) fulfilled the diagnostic criteria of AIP type 2 and were included in the study. A diagnosis of IBD was established in 29 patients (82.8%), ulcerative colitis in 17 (58.6%) and Crohn's disease in 11 (37.9%). Median follow-up was 54 months. AIP patients with IBD commonly presented with abdominal pain and/or acute pancreatitis at diagnosis, the latter was prevailing in concomitant and later IBD onset. These patients more frequently used steroids, but there were no differences in relapse rates. Concomitant onset of IBD was associated with the development of diabetes mellitus. There were no cases of colon or pancreatic malignancy during follow-up. In our systematic analysis, a total of 693 AIP type 2 patients were included from 24 single-center retrospective studies and 8 multicenter retrospective studies. A diagnosis of IBD was reported in 330 (47.8%) patients. Relapse rate was 20.0%. CONCLUSIONS: Clinical and radiological remission of AIP type 2 was high, while the cumulative incidence of relapse is around 20%. Our results show that concomitance of IBD imposes no obvious risk of a different disease course for AIP type 2.