A case of primary biliary cholangitis overlapping with type 2 autoimmune hepatitis.

A 42-year-old woman was admitted to our hospital with cholestatic liver injury. Serological examination revealed anti-mitochondrial M2 antibody positivity and anti-nuclear antibody and anti-smooth muscle antibody negativity. Histological examination of the first liver biopsy revealed chronic nonsuppurative destructive cholangitis with epithelioid granulomas. Ursodeoxycholic acid therapy successfully treated her cholestasis. Sixteen months later, she developed acute icteric hepatitis with elevation of serum aspartate and alanine aminotransferase levels. Anti-mitochondrial M2 positivity and anti-nuclear antibody and anti-smooth muscle antibody negativity persisted at that time. However, it became clear that anti-liver kidney microsomal type 1 antibody was positive. Histological examination of the second liver biopsy demonstrated scarce interface hepatitis and evident parenchymal inflammation and centrilobular zonal necrosis. Her liver biochemical test results promptly improved with the addition of prednisolone therapy. Considering the findings, she was diagnosed with primary biliary cholangitis-type 2 autoimmune hepatitis overlap syndrome. According to a literature review, this is an extremely rare autoimmune overlap syndrome.