ANTI-M4 ANTIBODIES MEASURED BY A SULFITE OXIDASE ELISA IN PATIENTS WITH BOTH ANTICENTROMERE AND ANTI-M2 ANTIBODIES

In this study the clinical features of patients with a serological ove rlap between scleroderma and primary biliary cirrhosis (PBC) were anal ysed. The entity was defined by the presence of both anticentromere an tibody (ACA) and anti-mitochrondrial antibodies to the M2 antigen, pyr uvate dehydrogenase. In addition the sera were assayed for anti-mitoch ondrial antibodies to the M4 antigen measured by an ELISA to sulphite oxidase (SO). First, anti-M2 was detected, not only in 58 out of 60 pa tients with PBC but also in eight out of 61 patients with ACA. These s era, together with sera from 53 normals and 99 from patients with vari ous connective tissue diseases were then evaluated for anti-SO, which has been proposed by Klein and Berg to be a marker of progressive live r disease. Again, a high proportion (62%) of sera from patients with P BC were positive for anti-SO, and three of the eight patients who had ACA and anti-M2 also reacted with SO. We subsequently identified and i ncluded for study a further 10 patients positive for ACA and anti-M2, making a total of 18 patients with this profile. Features of limited c utaneous scleroderma were present in 94% and evidence of liver disease in 56%. Eight out of the 18 patients had anti-SO, and of these four h ad PBC, two had abnormal biochemical liver function tests but two had no evidence of liver disease. These data confirm that detection of ant i-SO is limited to an anti-M2 subpopulation, and may be a marker for l iver involvement with prognostic significance in scleroderma patients with ACA.