Isolated variant of IgG4-sclerosing cholangitis masquerading as hilar cholangiocarcinoma — an enigmatic entity

Background IgG4-mediated sclerosing cholangitis (IgG4-SC) is an autoimmune disease that generally occurs in association with type 1 autoimmune pancreatitis (AIP). However, an isolated variant of IgG4-SC is a rare disease that can occur without concurrent AIP and closely mimics extrahepatic cholangiocarcinoma both clinically and radiologically. Case presentation Here, we report a case of an isolated variant of IgG4-SC, which was pre-operatively diagnosed as hilar cholangiocarcinoma. Pathological and immunohistochemical examination revealed features suggestive of IgG4-SC, which was confirmed by elevated serum IgG4 levels measured postoperatively. Conclusion Therefore, IgG4-SC should be carefully ruled out in patients presenting with isolated bile duct obstruction, before performing morbid surgical procedures.