Anti-mitochondrial M2 antibody-positive autoimmune hepatitis.

Anti-mitochondrial M2 antibody (AMA-M2) is specific to primary biliary cirrhosis (PBC), but can also be found in certain patients with autoimmune hepatitis (AIH). Effective methods of differentiating between PBC and AIH are required, as their clinical course and management are different. Titers of AMA-M2 were analyzed before and after follow-up in patients with PBC or AIH. Patients who underwent liver biopsy and were diagnosed with either AIH (10 patients) or PBC (3 patients) were enrolled in the study. The AMA-M2 antibody titers of these patients were analyzed upon hospital admission. AMA-M2 reacted with the pyruvate dehydrogenase complex-E2, branched-chain 2-oxo acid dehydrogenase complex and 2-oxoglutaric acid dehydrogenase complex in the assay utilized for this study. The cut-off value for AMA-M2 was 5. Six AIH patients were AMA-M2(-) and 4 were AMA-M2(+). The titer for the AIH patients who were AMA-M2(+) was 24.8±14.8, compared with 324±174 in the patients with PBC (P=0.0138). Three AMA-M2(+) AIH patients were followed-up after liver biopsy. The AMA-M2 levels had decreased in all 3 patients, becoming undetectable in 2 of them. In conclusion, certain patients with AIH in this study were found to be AMA-M2(+), but the titers were significantly lower than those in the patients with PBC. At follow-up, the AIH patients exhibited decreased AMA-M2 titers.