Diagnosis of Immunoglobulin G4-Related Sclerosing Cholangitis

SC) is a characteristic type of SC with increased serum IgG4 levels and dense infiltration of IgG4-positive plasma cells with extensive fibrosis in the bile duct wall.1 IgG4-SC is now recognized within the spectrum of systemic IgG4-related diseases. IgG4-SC is well resolved by steroid therapy, which is a characteristic feature of IgG4-related disease. IgG4-SC is frequently associated with type 1 autoimmune pancreatitis (AIP) and IgG4-related sialadenitis; retroperitoneal fibrosis can also occasionally be observed in IgG4-SC. However, some IgG4-SC cases do not involve any other organs. The cholangiographic abnormalities observed in IgG4-SC may resemble those of primary sclerosing cholangitis (PSC) and hilar cholangiocarcinoma. Since obstructive jaundice is frequently observed in IgG4-SC, and IgG4-SC is most common in elderly men, the differential diagnosis compared to that for hilar cholangiocarcinoma is sometimes very difficult. Secondary SC also should be ruled out. An elevated serum IgG4 level is a characteristic feature of IgG4-SC and can effectively detect patients with IgG4-SC.2 However, IgG4-SC patients without pancreatic involvement displayed no marked increase in serum IgG4 levels compared to patients with AIP-associated IgG4-SC. Even though an IgG4 cutoff level of 135 mg/dL is widely used as part of the diagnostic criteria for AIP, a few reports concerning the IgG4 cutoff level in the diagnosis of IgG4-SC have been published.3,4