Autoimmune pancreatitis: a message from Japan.

Autoimmune pancreatitis (AIP) is a unique form of chronic pancreatitis generally observed in aged people and characterized by the presence of autoantibodies,(1-3) elevated levels of immunoglobulins,(4) enlargement of the pancreas (diffuse or focal) on ultrasonography (US) or computed tomography (CT),(1-3,5) diffuse narrowing of the main pancreatic duct (MPD) with an irregular wall,(1,3,5-8) and pathologic features of dense lymphoplasmacytic inflammation and fibrosis, as well as a favorable response to steroid therapy.(1-3,5,8) The clinical findings in AIP include obstructive jaundice secondary to biliary stenosis, mild epigastralgia, and diabetes mellitus. The clinical, laboratory, and radiological features respond promptly to oral steroid therapy.(1-3,5,6,8) Although prompt response to oral steroid therapy may be helpful in the differential diagnosis of AIP, careful imaging studies are necessary to exclude cancer of the pancreas or common bile duct (CBD).