Clinical and pathophysiological issues associated with type 1 autoimmune pancreatitis

In 1995, Yoshida and colleagues proposed the concept of ‘autoimmune pancreatitis’ (AIP). Recently, it is accepted that the existence of two subtypes of AIP—type 1, which involves immunoglobulin G4 (IgG4) as the pancreatic manifestation of IgG4-related disease (IgG4-RD), and type 2, which is characterized by granulocytic epithelial lesions. Type 2 AIP is thought to be rare in Japan. In 2011, the International Consensus Diagnostic Criteria (ICDC) for autoimmune pancreatitis was proposed. In Japan, the clinical diagnostic criteria of AIP 2011 was proposed by the Japan Pancreas Society (JPS) and the Research Committee of Intractable Diseases of the Pancreas. The JPS 2011 is based on ICDC and a simplified checklist of items to diagnose type 1 AIP. Although recent progress in type 1 AIP has resolved clinical features, diagnosis, treatment, and pathogenesis, many clinical and basic issues still remain unclear. Here, we provide an overview of the recent clinical and basic issues associated with type 1 AIP.