Autoimmune pancreatitis. Diagnosis and therapy

Autoimmune pancreatitis (AIP) has been established for more than 15 years as a disease entity of chronic pancreatitis. Although the autoimmune etiology is well established AIP is still an enigmatic disease. Morphological hallmarks of the disease are narrowing of the pancreatic duct system and frequently even narrowing of the bile duct by periductal lymphoplasmocytic inflammation. In cases of more localized inflammation obstructive jaundice due to a mass-forming lesion in the pancreatic head may mimic pancreatic ductal adenocarcinoma. Therefore, even in tertiary referral center, AIP patients underwent pancreatic surgery for suspected pancreatic cancer due to misclassification. Histopathologically, the disease can be differentiated into lymphoplasmacytic sclerosing pancreatitis (LPSP) with IgG4-positive cells or idiopathic ductocentral chronic pancreatitis (IDCP) with granulocyte epithelial lesions and eosinophils. Recently, LPSP has been coined AIP type 1 and IDCP as AIP type 2 following a recent consensus conference. Serologically, patients may present with elevated serum IgG and IgG4 levels. Additionally, autoantibodies have been described targeting ductal and acinar antigens. Association with other autoimmune manifestations in a wide range of organs is relatively frequent. In most cases, autoimmune pancreatitis responds to steroid treatment very quickly, which is of specific importance when considering the differential diagnosis of pancreatic cancer.