A 12-year-old girl with antimitochondrial antibody-positive autoimmune hepatitis.

Autoimmune hepatitis is rare and, in childhood, is typically associated with either the nuclear and/or smooth muscle antibody or with the liver kidney microsomal type 1 antibody. Antimitochondrial antibodies, which are considered diagnostic of primary biliary cirrhosis, have not been described in the paediatric age. We report for the first time a 12-year-old girl with antimitochondrial-antibody-positive autoimmune hepatitis. Antimitochondrial antibody positivity was determined by immunofluorescence and immunoblot. The patient's age, clinical, biochemical and histological features and response to immunosuppressive treatment support the diagnosis of autoimmune hepatitis.