Immunoglobulin G4 Cholangiopathy Masquerading as a Klatskin Tumor: An Interesting Case.

Immunoglobulin G4 (IgG4) cholangiopathy is used to describe regional biliary involvement in a systemic fibro-inflammatory and infiltrative disease, IgG4-related disease. Occasionally, it tends to present with localized disease leading to an extensive workup to rule out malignancy and infections, especially since IgG4-related disease is an uncommon entity. Herein, we present a case of a 68-year-old male who presented with pruritus and steatorrhea with imaging studies revealing a biliary hilar mass concerning for malignancy. Subsequent extensive testing was inconclusive of malignancy and finally noted to have elevated IgG4 levels as part of a broader workup. The patient was started on prednisone with the resulting improvement in his symptoms and the imaging findings.