Clinicopathological features of type 2 autoimmune pancreatitis in Japan: Results of a multicenter survey

Objective: The aim of the study was to clarify clinicopathological features of type 2 autoimmune pancreatitis (AIP) in Japan; a multicenter survey was carried out. Methods: The first screening collected patients with pancreatitis whose pancreatic tissue samples were available and who fulfilled at least 1 of the following 3 criteria as possible type 2 AIP: (1) histological presence of granulocytic epithelial lesion, (2) age of 50 years or younger, and (3) association of ulcerative colitis, Sjogren syndrome, and/or primary biliary cirrhosis. Patients with histologically confirmed type 1 AIP were also collected as a control. Clinical information was gathered by questionnaire. Results: A histological re-evaluation identified 8 patients with type 2 AIP and 20 with type 1 AIP. Three of the latter had intralobular neutrophilic infiltration. Factors more frequent in type 2 included age younger than 40 years, abdominal pain, and elevation of serum amylase and lipase, whereas patientswith type 1 more frequently showed jaundice, elevated serum IgG and IgG4, presence of autoantibodies, association of IgG4-related disease, sclerosing cholangitis and diabetes mellitus, and imaging findings of intrapancreatic biliary stenosis and extrapancreatic biliary dilatation. Conclusions: The clinical features of type 2 AIP in Japan were similar to those of western countries. Intralobular neutrophilic infiltration in type 1 is a potential pitfall, especially in the biopsy-based diagnosis.