Current concepts in the diagnosis and treatment of type 1 and type 2 autoimmune pancreatitis

Since the 1990s, autoimmune pancreatitis (AIP) has been increasingly recognized as a special type of chronic pancreatitis. Clinically, AIP patients commonly present with jaundice, weight loss and abdominal pain. Radiologically, there is diffuse or focal enlargement of the pancreas, often with narrowing of the pancreas and bile duct. Histologically, AIP is characterized by periductal infiltrates of lymphocytes and plasma cells, cellular fibrosis and obliterative phlebitis. Recently, two types of AIP were distinguished and called type 1 and type 2 AIP. They share the symptomatology and some histopathological features such as periductal lymphoplasmacytic infiltrate and storiform fibrosis, but differ in a particular duct change, called granulocytic epithelial lesion, which characterizes type 2 AIP. In addition, type 2 AIP usually has none or very few (