S5815 Painless Obstructive Jaundice Suspected of Malignancy: A Case of IgG4-Related Hepatitis

Introduction: IgG4-related disease is a systemic inflammatory condition characterized by infiltration of various organs, including the liver, by IgG4-positive plasma cells. IgG4-related hepatitis is rare and often mimics primary sclerosing cholangitis and autoimmune hepatitis, complicating diagnosis. It is more common in men than women (2.2:1). Early recognition is essential to prevent liver damage, as the disease typically responds well to corticosteroids. A full diagnostic workup is important to rule out malignancy. Case Description/Methods: A 70-year-old woman with a family history of pancreatic cancer presented with fatigue, weight loss, jaundice, elevated liver enzymes (aspartate aminotransferase 97 U/L, alanine aminotransferase 62 U/L, alkaline phosphatase 954 U/L), and total bilirubin of 10 mg/dl. Viral and autoimmune markers, including antinuclear antibody and SMA, were unremarkable. Computed tomography scan and magnetic resonance imaging demonstrated a 6 cm hepatic mass with lymphadenopathy prompting further evaluation with endoscopic ultrasound (EUS) and endoscopic retrograde cholangiopancreatography (ERCP). EUS revealed normal hepatic parenchyma with dilated intrahepatic duct. Fine needle biopsy (FNB) EUS obtained at the transition site from biliary stenosis to intrahepatic biliary dilation. ERCP with cholangioscopy revealed biliary stenosis at the common hepatic duct, 2 intrahepatic biliary stents placed for decompression. Liver biopsy demonstrated portal and periportal lymphoplasmacytic infiltrates with fibrosis and more than 50 IgG4-positive plasma cells per high-power field, confirming IgG4-related hepatitis. She was started on 40 mg prednisone with plans for repeat Imaging within 3 months with follow up ERCP stent removal. Discussion: We present a case of IgG4-related disease mimicking malignant obstructive jaundice. The diagnostic approach and follow-up are essential to confirm the diagnosis. Liver biopsy typically reveals a dense lymphoplasmacytic infiltrate with numerous IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis. It is important to distinguish this from autoimmune hepatitis, as treatments differ. Corticosteroids remain the mainstay of therapy and generally yield good clinical response, though relapses may occur. Early diagnosis and treatment are critical to avoid cirrhosis or liver failure. In biliary involvement, ERCP may be necessary for decompression. Ongoing research is needed to refine diagnostic criteria and optimize long-term care. Follow-up imaging after treatment helps confirm lesion resolution and rule out neoplasia.