A rare case of IgG4-related sclerosing cholangitis followed by rapid subsequent diagnosis of cholangiocarcinoma.

Immunoglobulin G4 (IgG4)-related sclerosing cholangitis (IgG4-SC) is a rare condition with symptoms often mimicking malignancy, infection, or other autoimmune diseases. This case report describes the unique case of a 62-year-old male initially diagnosed with IgG4-SC, followed by subsequent diagnosis of cholangiocarcinoma. Biliary tract cancer in the setting of IgG4 related disease has been previously described; however, this patient course is novel as it encompasses the spectrum of challenges in IgG4-SC management, including diagnostic uncertainty, risk of infection with immunosuppressive agents, and development of malignancy diagnosed shortly following IgG4-SC diagnosis. We review the literature of management, outcomes, and malignancy risk and furthermore, highlight a promising recent therapy in treatment of IgG4 related disease, inebilizumab.