Characterization of the overlap syndrome of primary biliary cirrhosis (PBC) and autoimmune hepatitis: evidence for it being a hepatitic form of PBC in genetically susceptible individuals.

Some patients with autoimmune liver disease present with a clinical and/or histological picture showing characteristic findings of both autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC). Various names, mostly overlap syndrome, have been used to describe these cases, which have thus far not been more closely characterized. The aim of this study was the comparison of 20 patients with overlapping features to representative patients considered suffering from typical AIH or typical PBC (20 patients in each group). We found these patients to indeed show a very mixed picture of both conditions biochemically, serologically, and histologically. However, closer analysis suggested that all of these patients were primarily suffering from PBC as all of them had at least either bile duct destruction on histology or anti-M2 positive antimitochondrial antibodies (AMA). We suggest that these PBC patients because of their genetic susceptibility, evidenced by the AIH-characteristic histocompatibility leukocyte antigen (HLA) type B8, DR3, or DR4, developed a more hepatitic picture. Response to immunosuppressive therapy was excellent. We propose that the name "overlap syndrome" be abandoned for "PBC, hepatitic form." These observations not only have pathophysiological implications, but also suggest that therapy of PBC should be guided by the degree of biochemical and histological hepatic involvement.