Background: Anti-mitochondrial antibody is the diagnostic hallmark of primary biliary cirrhosis. Its role in the aetiology of primary biliary cirrhosis is controversial.
Methods: Two cases of neonatal hepatitis seropositive for anti-mitochondrial antibody are described. Anti-mitochondrial antibody Ig isotype and epitopic specificity were investigated by immunofluorescence and enzyme immunoassays.
Results: In both infants anti-mitochondrial antibody was of the G class, mainly G1 and G3 subclasses, and reacted with two synthetic peptides reproducing major M2 epitopicregions: innerlipoyl domain pyruvate dehydrogenase complex (PDC)-E2(162-176) and PDC-E3 binding protein (PDC-E3BP)86-100. One infant also reacted with outer lipoyl domain PDC-E2(35-49), and 2-oxoglutarate dehydrogenase complex (OGDC)-E2(99-113). An identical pattern of reactivity was present in their mothers, indicating the maternal origin of the antibodies. Anti-mitochondrial antibody disappeared in the infants with the disappearance of the liver pathology.
Conclusions: The simultaneous disappearance of hepatitis and anti-mitochondrial antibody in the infants suggests a possible causal link between the two.