Counterpoint: Biliary Manifestations in Autoimmune Pancreatitis

Abstract

IgG4-related sclerosing cholangitis (IgG4-SC) and autoimmune pancreatitis (type 1 AIP) are the biliary and pancreatic manifestations, respectively, of IgG4-related disease (IgG4-RD). IgG4-SC, like primary sclerosing cholangitis (PSC), is characterized by biliary strictures that can mimic those seen in pancreatic cancer (solitary distal CBD stricture), cholangiocarcinoma (hilar or proximal extrahepatic bile duct bile duct strictures), or PSC (diffuse extra- and/or intrahepatic strictures). The distinction between IgG4-SC and the diseases it mimics is not always easy. Despite its association with IgG4, IgG4-SC cannot be distinguished from PSC based on serum IgG4 elevation (10–15 % of PSC and cholangiocarcinoma also have elevated serum IgG4) or tissue infiltration with IgG4+ plasma cells (20–30 % of PSC and cholangiocarcinoma also show this feature). The presence of concomitant AIP is the best predictor of IgG4-SC. Inflammation in IgG4-SC is exquisitely sensitive to steroids; however a scarred biliary tree may never return to normal despite resolution of inflammation. Since IgG4-SC has a higher predilection for relapse, maintenance therapy is often needed. The options for maintenance therapy include low-dose steroids, steroid sparing immunomodulators such as azathioprine or B-cell depletion therapy with rituximab. Rituximab has shown promise as a single agent that can induce and maintain remission.