Anti-mitochondrial antibodies in patients with Graves' disease may not signify primary biliary cirrhosis.

Two patients with Graves' disease were incidentally found to have anti-mitochondrial antibodies by immunofluorescence in the absence of symptoms, clinical signs or biochemical evidence of liver dysfunction. Anti-mitochondrial antibody titres became undetectable in both patients on follow-up. Screening of the patients' sera by immunoblotting against the purified antigens of the M2 complex was negative. We conclude that in these cases, anti-mitochondrial antibodies detected by immunofluorescence were directed against antigens other than the primary biliary cirrhosis-associated M2 complex and therefore did not signify subclinical primary biliary cirrhosis.