Clinical Significance of Extrapancreatic Lesions in Autoimmune Pancreatitis

Objectives: To clarify the frequency and clinical significance of extrapancreatic lesions in autoimmune pancreatitis (AIP). Methods: The frequency and clinical characteristics of extrapancreatic lesions during the clinical course of AIP were investigated retrospectively in 64 patients with AIP. The predictive factors for relapse of AIP at clinical onset were also examined. Results: Extrapancreatic lesions occurred in 95% (61/64) during the clinical course of AIP. The frequencies of sclerosing cholangitis, sclerosing sialadenitis, retroperitoneal fibrosis, and mediastinal or hilar lymphadenopathy were 84% (54/64), 23% (15/64), 16% (10/64), and 77% (27/35), respectively. Patients with sclerosing sialadenitis or extrapancreatic bile duct sclerosing cholangitis had a significantly higher serum immunoglobulin G concentration than those without (P = 0.005 and P = 0.016, respectively). Univariate analysis revealed that sclerosing sialadenitis (P = 0.005), diffuse pancreatic ductal changes (P = 0.028), and a high serum immunoglobulin G concentration (P = 0.030) at clinical onset of AIP were significant predictive factors for relapse. Multivariate analysis revealed that diffuse pancreatic ductal changes (P = 0.005) and sclerosing sialadenitis (P = 0.012) were significant independent predictive factors for relapse of AIP. Conclusions: The frequency of extrapancreatic lesions with AIP during the clinical course was high. The presence of sclerosing sialadenitis at clinical onset is a significant predictive factor for relapse of AIP.