An asymptomatic 70-year-old Hispanic woman with type 2 diabetes was found in 2004 to have an AST of 132 U/L, ALT 146 U/L, alkaline phosphatase 1107 U/L, total serum bilirubin 3.5 mg/dL, and albumin 2.9 g/dL. Viral hepatitis testing was negative. Serum IgG, IgA, and IgM were all elevated, antimitochondrial antibody was weakly positive, and antinuclear antibody was negative. Liver biopsy was reported to show "evolving cirrhosis with marked lymphoid hyperplasia." Although the indication was nowhere stated, she was prescribed ursodeoxycholic acid 500 mg b.i.d, on which her biochemical tests initially improved. One year later she developed itching and jaundice. Imaging studies revealed multiple gallstones. An MRCP was suggestive of cirrhosis with a questionable common bile duct stricture, and she underwent ERCP with removal of gallbladder and common bile duct stones and placement of a biliary stent. A periampullary mass, which proved to be a somatostatinoma, was excised in 2006 via an open laparotomy, at which the stent was removed and a second liver biopsy performed. It was reported as showing chronic active hepatitis, activity stage 2, and fibrosis grade 3 with bridging. Her subsequent course was complicated by recurrent bleeding from small bowel arteriovenous malformations. Seen for the first time at Columbia University Medical Center in January 2007, she complained of continuing pruritus. AST was 69 U/L, ALT 43 U/L, alkaline phosphatase 491 U/L, and total bilirubin 3.3 mg/dL. Serum albumin was 2.6 g/dL. Antinuclear antibodies, negative in 2004, were now positive at 1:320, and antimitochondrial M2 antibodies were strongly positive. Serum IgG and IgA, but NOT IgM, were elevated. Review of her outside liver biopsies revealed features of primary biliary cirrhosis (PBC) in the first, and of both PBC and autoimmune hepatitis (AIH) in the second. The patient exhibits an overlap syndrome, in which both histologic and serologic features of AIH evolved in a setting initially most suggestive of PBC alone. The phenomenon of autoimmune overlap syndromes is discussed.