Abstract and Introduction
Abstract
Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis characterised clinically by frequent presentation with obstructive jaundice, histologically by a lymphoplasmacytic infiltrate with fibrosis, and therapeutically by a dramatic response to steroids. When so defined, AIP can be sub-classified into two subtypes, 1 and 2. Recent international consensus diagnostic criteria for AIP have been developed for diagnosis of both forms of AIP. Type 1 AIP is the pancreatic manifestation of a multiorgan disease, recently named IgG4-related disease. Little is known about the pathogenesis of either form of AIP. Despite frequent association of type 1 AIP with elevated serum IgG4 levels and infiltration with IgG4-positive plasma cells, it is unlikely that IgG4 plays a pathogenic role in AIP. Type 1 AIP responds to steroids, but there needs to be consensus on treatment regimens for induction and therapeutic end points. Relapses are common, but can be reduced by long-term use of low-dose steroids. Recent reports suggest that immunomodulators (azathioprine, 6-mercaptopurine and mycophenolate mofetil), as well biological agents (the antibody to CD20, rituximab) may have a role in maintaining remission in relapsing type 1 AIP. Future studies should clarify the best management options for treatment of relapses and maintenance of remission. Type 2 AIP is a pancreas-specific disorder not associated with IgG4. It presents in younger individuals equally with obstructive jaundice and pancreatitis. The inflammatory process responds to steroid therapy; relapses are uncommon. The clinical spectrum and long-term outcomes of medically treated type 2 AIP are still being evaluated.
Introduction
Autoimmune pancreatitis (AIP) is a benign fibroinflammatory disease of the pancreas that has recently attracted worldwide attention. The term AIP was first proposed in 1995 for a steroid-responsive pancreatic inflammatory disease; since then it has become recognised as a distinct clinicopathological entity. Patients with AIP often present with painless obstructive jaundice mimicking pancreatic cancer, which is far more common and has a dismal prognosis. As AIP dramatically responds to steroids, a correct and timely diagnosis of AIP saves unnecessary surgery. However, AIP sometimes relapses and its long-term prognosis is unknown. Review of worldwide data indicates that AIP comprises two subtypes, presently termed types 1 and 2. Here we review the pathology, pathogenesis, clinical features, diagnosis, treatment and natural history of types 1 and 2 AIP.