| [ Summary ] |
Autoimmune pancreatitis (AIP) is a distinct type of pancreatitis presumably caused by autoimmune mechanisms and is characterized by a high serum IgG4 concentration and IgG4‒bearing plasma cell infiltration in the affected organ. AIP is complicated with various extrapancreatic involvements, which also show close association with IgG4. Based on this close association with IgG4, AIP and its extra‒pancreatic lesions have been integrated into the systemic disease concept of IgG4‒related disease (IgG4‒RD), and AIP is now regarded as a major member of IgG4‒RD. The characteristic pathological feature of AIP is lymphoplasmacytic sclerosing pancreatitis (LPSP), whereas another pathological type of AIP characterized by granulocyte infiltration has been reported in western countries, namely, idiopathic duct‒centric chronic pancreatitis (IDCP) or AIP with granulocyte epithelial lesion (GEL). AIP was later classified as type 1 or type 2 based on the pathological subtypes of LPSP and IDCP/GEL, respectively. Clinical features of type 2 AIP are vastly different from those of type 1, showing a young and middle age preponderance, no gender bias, frequent abdominal pain or complication of acute pancreatitis, a low prevalence of jaundice as compared with type 1, no correlation with IgG4 and complicating inflammatory bowel disease. |