Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) is a subcategory of chronic pancreatitis that is highly responsive to steroids. The term was first proposed in 1995 by Yoshida and colleagues, and since its discovery, the diagnosis of AIP has dramatically increased. AIP is a chronic fibroinflammatory disease characterized by lymphoplasmacytic infiltrates and fibrosis on histology. There are two distinct subtypes: type 1 AIP is the pancreatic manifestation of a systemic serum immunoglobulin G subtype 4–related disease (IgG4-RD) and type 2 AIP is described clinically as idiopathic duct-centric pancreatitis and has no association with IgG4. Clinically, AIP presents most commonly as obstructive jaundice in type 1 AIP and can present as acute pancreatitis in type 2 AIP. The diagnostic criteria include histology, imaging findings, and responsiveness to steroids as well as laboratory findings and other organ involvement. The mainstay of treatment is steroid therapy, with immunomodulators such as rituximab used for maintenance or relapsing disease. Long-term complications of AIP include pancreatic insufficiency and are often associated with relapsing disease. This review contains 45 references, 1 figure, and 2 tables. Key Words: autoimmune pancreatitis, chronic pancreatitis, EUS-guided biopsy, IgG4, immunomodulatory, obstructive jaundice, pancreas mass, steroid