Autoimmune pancreatitis

The purpose of this review is to provide a concise view of the existing knowledge of autoimmune pancreatitis (AIP) for practicing clinicians. AIP is a rare disease whose recognition and understanding are evolving. It is a type of chronic pancreatitis that often presents as obstructive jaundice, has a distinctive histology, and is exquisitely sensitive to steroid therapy. This form of chronic pancreatitis has a unique clinical, biochemical, and radiological profile. The term "AIP" encompasses two subtypes: types 1 and 2. Type 1 AIP is the pancreatic manifestation of a systemic fibro-inflammatory disease called immunoglobulin G4-associated systemic diseases. Type 2 AIP has been shown to be associated with inflammatory bowel disease. Existing criteria are geared towards the diagnosis of type 1 AIP. At present, pancreatic histology is a requirement for the definitive diagnosis of type 2 AIP. AIP can mimic most other pancreatic diseases in its presentation, but in clinical practice, it often has to be differentiated from pancreatic cancer. There are established criteria and algorithms not only to diagnose AIP, but also to differentiate it from pancreatic cancer. The utility of these algorithms and the approach to management are discussed here.