Diagnostic criteria for autoimmune pancreatitis.

Autoimmune pancreatitis (AIP), a particular type of pancreatitis, is thought to have an autoimmune etiology; it is recognized as a distinct entity worldwide. AIP has many characteristic clinical, serologic, morphologic, and histopathologic features. In the absence of a diagnostic serologic marker for AIP, AIP should be diagnosed on the basis of combination of characteristic findings. AIP responds dramatically to steroid therapy; thus, accurate diagnosis of AIP can avoid unnecessary laparotomy or resection. It is important not to misdiagnose pancreatic cancer as AIP, and not to misdiagnose AIP as pancreatic cancer. Currently, 3 sets of major diagnostic criteria for AIP have been proposed in Japan, Korea, and the United States. The Japanese criteria are based on the minimum consensus features of AIP and aim to avoid misdiagnosis of malignancy. When response to steroid therapy is added to the criteria, the diagnostic sensitivity is increased. However, the use of a steroid trial in cases where differentiation from malignancy is an issue may result in delaying pancreatic cancer surgery, which could lead to cancer progression in several cases. Thus, given that AIP is an IgG4-related systemic disease, an additional criterion can be recommended to the Japanese diagnostic criteria: IgG4-immunostaining of biopsied extrapancreatic lesions such as the major duodenal papilla, the bile duct, or the minor salivary gland. It is also time for an international consensus on AIP.