Differences in Clinical Profile and Relapse Rate of Type 1 Versus Type 2 Autoimmune Pancreatitis

Background & Aims Autoimmune pancreatitis (AIP) has been divided into subtypes 1 (lymphoplasmacytic sclerosing pancreatitis) and 2 (idiopathic duct centric pancreatitis). We compared clinical profiles and long-term outcomes of types 1 and 2 AIP. Methods We compared clinical presentation, relapse, and vital status of 78 patients with type 1 AIP who met the original HISORt criteria and 19 patients with histologically confirmed type 2 AIP. Results At presentation, patients with type 1 AIP were older than those with type 2 AIP (62 ± 14 vs 48 ± 19 years; P < .0001) and had a greater prevalence of increased serum levels of immunoglobulin G4 (47/59 [80%] vs 1/6 [17%]; P = .004). Patients with type 1 were more likely than those with type 2 to have proximal biliary, retroperitoneal, renal, or salivary disease (60% vs 0; P < .0001). Inflammatory bowel disease was associated with types 1 and 2 (6% vs 16%; P = .37). During median clinical follow-up periods of 42 and 29 months, respectively, 47% of patients with type 1 and none of those with type 2 experienced a relapse. In type 1 AIP, proximal biliary involvement (hazard ratio [HR], 2.12; P = .038) and diffuse pancreatic swelling (HR, 2.00; P = .049) were predictive of relapse, whereas pancreaticoduodenectomy reduced the relapse rate (vs the corticosteroid-treated group; HR, 0.15; P = .0001). After median follow-up periods of 58 and 89 months (types 1 and 2, respectively), the 5-year survival rates for both groups were similar to those of the age- and sex-matched US population. Conclusions Types 1 and 2 AIP have distinct clinical profiles. Patients with type 1 AIP have a high relapse rate, but patients with type 2 AIP do not experience relapse. AIP does not affect long-term survival.