Ectasia to Ecstatic: A Case Report of Immunoglobulin G4-related disease Masquerading as Primary Sclerosing Cholangitis

Immunoglobulin G4-sclerosing cholangitis (IgG4-SC) is a rare fibroinflammatory disease that involves the biliary duct and can often mimic Primary Sclerosing Cholangitis (PSC). It is a chronic disease that has the potential to progress to cirrhosis if left untreated. Obtaining a biopsy and serum IgG levels are crucial for diagnosis and understanding the extent of the disease. Here, we present a case of IgG4-SC in a woman with no prior biliary history, who initially presented with mid-abdominal pain and jaundice. She underwent ERCP, which demonstrated a distal biliary stricture requiring stenting, although imaging demonstrated concern for autoimmune cholangitis given the diffuse ectasia seen. Serum IgG4 levels were found to be four times the upper limit of normal and liver biopsy was consistent with IgG4-related disease, so the patient was started on glucocorticoids with a positive response. IgG4-SC can be a difficult diagnosis to obtain and often mimics other pathologies, so it is an important diagnostic consideration given that it can typically be easily treated within the correct clinical context.