S3562 IgG4-Related Hepatobiliary Disease Presenting as Biliary Stricture and Hepatic Mass: A Delayed Diagnosis

Introduction: Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disorder that can affect multiple organ systems, including the hepatobiliary system, manifesting as conditions such as IgG4-Related Sclerosing Cholangitis (IgG4‐SC). IgG4‐SC can manifest as biliary strictures and pseudotumor. It poses diagnostic challenges by mimicking cholangiocarcinoma and primary sclerosing cholangitis, leading to misdiagnosis and unnecessary interventions. Accurate diagnosis of IgG4-SC relies on a combination of clinical, radiological, and histopathological findings. Case Description/Methods: We present the case of a 70-year-old gentleman with a history of hepaticojejunostomy performed over 15 years ago for a presumed Klatskin tumor at an outside hospital. At that time, he was found to have elevated liver enzymes. Computed tomography imaging revealed a liver lesion and a stricture at the confluence of the right and left hepatic ducts with biliary dilatation, concerning for Klatskin tumor. Endoscopic retrograde cholangiopancreatography (ERCP) with biliary stent placement was performed, but brushings were negative for malignancy. He ultimately underwent hepaticojejunostomy and remained stable without further treatment. Fourteen years later, laboratory tests revealed elevated liver enzymes, consistent with a cholestatic pattern. Magnetic resonance cholangiopancreatography (MRCP) demonstrated intrahepatic biliary dilation and a stricture at the choledochojejunostomy site. He underwent percutaneous transhepatic cholangiography and liver biopsy; imaging revealed a stricture of the segment 5 ducts, and biopsy showed portal and lobular inflammation with ductular proliferation and fibrosis. Autoimmune testing revealed a positive ANA and elevated smooth muscle antibody, while immunoglobulin testing showed elevated IgM and IgG4 levels. Retrospective review of his 2011 pathology also revealed features suggestive of IgG4-RD, indicating the diagnosis was likely missed. Given laboratory, imaging and histopathological findings, he was diagnosed with IgG4‐SC with autoimmune hepatitis overlap. He was initiated on corticosteroids, with improvement in liver biochemistries. Discussion: The diagnosis of IgG4‐SC is difficult due to its ability to mimic malignant and benign cholangiopathies. This case highlights the importance of clinical suspicion in patients with biliary strictures and tumors. The HISORt criteria provide a comprehensive framework for diagnosis, incorporating histopathological, imaging, serological, and clinical findings, as well as response to therapy. Early recognition avoids misdiagnosis and unnecessary surgery.