IgG4-SC는 type 1 AIP의 가장 흔한 췌장 외 발현으로 type 1 AIP 환자의 약 70%에서 발생하는 것으로 보고되었고 드물게 단독으로 발생하기도 한다. IgG4-SC의 진단은 임상적으 로 매우 중요한데, 이는 영상 소견상 담관암과의 감별이 어렵기 때문이다. IgG4-SC의 경우, 스테로이드 투여로 회복될 수 있다는 점에서 그 의의가 크다.
IgG4-related sclerosing cholangitis (IgG4-SC) represents a rare but clinically challenging differential diagnosis in patients with biliary strictures which can be mistaken for cholangiocarcinoma. We present a case of a 73-year-old male presented with abdominal discomfort and weight loss. Biliary images showed long-segment luminal narrowing of extrahepatic bile duct associated with prominent enhanced wall thickening, but luminal patency was preserved. Pancreatic images revealed segmental irregular narrowing of main pancreatic duct without upstream duct dilatation. His liver function tests and CA19-9 level were normal. Putting all findings together, IgG4-SC associated with autoimmune pancreatitis was strongly suspected. However, endobiliary biopsy of extrahepatic bile duct revealed adenocarcinoma which was not resectable due to celiac axis involvement. Because there is an overlap in biliary imaging findings between IgG4-SC and cholangiocarcinoma, biopsy is essential for adequate differential diagnosis. We present a case of cholangiocarcinoma masquerading as IgG4-SC based on clinical and imaging findings.