Clinical implications of antimitochondrial antibody seropositivity in autoimmune hepatitis: a multicentre study

Antimitochondrial antibody (AMA) positivity is the serological marker of primary biliary cholangitis (PBC), but can also be sporadically detected in autoimmune hepatitis (AIH). Little is known about the clinical significance of AMA in AIH.We recruited 47 AMA-positive AIH cases from several centres and compared them with 264 well-characterized Italian AIH patients. Cases with any features of PBC were excluded.In univariate analysis, AMA-positive AIH patients were older (46 vs. 36, P=0.002) and more responsive to immunosuppression (74 vs. 59%, P=0.05), but no differences were observed between the two groups after logistic regression using AMA as a dependent variable. None of the AMA-positive AIH patients showed signs of evolving PBC features after a median follow-up of up 47 months. AMA was detected in combination with all serological AIH markers except antiliver kidney microsome type 1 and antiliver cytosol type 1. AMA was the only marker of autoimmunity in eight cases.We found no differences between AIH with and without AMA. The groups had similar clinical, biochemical and histological features. AMA-positive AIH patients did not evolve towards PBC. In some cases, AMA was the only autoantibody.