Advances in IgG4-related pancreatobiliary diseases.

Autoimmune pancreatitis is an unusual form of pancreatitis that is histologically characterised by a massive infiltration of lymphocytes and IgG4-positive plasma cells and storiform fibrosis. The disease is recognised as a pancreatic manifestation of IgG4-related disease. IgG4-related sclerosing cholangitis is a biliary counterpart that is typically associated with autoimmune pancreatitis. Two parallel immunological responses are thought to underlie the pathophysiology of these diseases: a pro-inflammatory, tissue-destructive process and an anti-inflammatory feedback response, which probably relates to IgG4 production. These diseases should be differentiated from conditions with a similar presentation (eg, pancreatobiliary malignancy, primary sclerosing cholangitis) by comparison of serum IgG4 concentration, imaging features, other organ involvement, histology, and steroid responsiveness. Corticosteroids are first-line drugs, although rituximab has been shown to effectively deplete B cells in IgG4-related disease. Although the risk of relapse is high, no standardised treatment protocol exists for relapsed cases.