IgG4-related Inflammatory Pseudotumor of the Gallbladder Associated with Autoimmune Pancreatitis

Abstract

A 55-year-old man presented with epigastric pain. CT examination showed diffuse enlargement of the pancreas, stricture of the distal common bile duct and a 20-mm sessile tumor located in the fundus of the gallbladder. In addition to these findings, the patient’s serum IgG4 level was elevated. Autoimmune pancreatitis was diagnosed. Bile duct biopsy showed no malignancy. The cause of the common bile duct stricture was thought to be IgG4-related sclerosing cholangitis associated with autoimmune pancreatitis. However, extended cholecystectomy was performed because gallbladder cancer could not be excluded. Histopathological findings revealed no malignancy, but storiform fibrosis and infiltration of IgG4+ plasma cells were discovered. The final diagnosis was IgG4-related inflammatory pseudotumor of the gallbladder. Autoimmune pancreatitis is considered to be one of the major manifestations of IgG4-related disease. Various extra-pancreatic lesions associated with autoimmune pancreatitis have been reported, but reports of inflammatory pseudotumor of the gallbladder are extremely rare.