AUTOIMMUNITY TO ALPHA-MYOSIN IN A SUBSET OF PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY

Objective - To use an enzyme linked immunoassay (ELISA) technique to a ssess frequency and disease specificity of anti-alpha-myosin antibodie s in patients with dilated cardiomyopathy and their relatives. Methods - Evaluation was performed on sera (dilution 1/320) from 123 consecut ive patients with dilated cardiomyopathy (WHO criteria) (age 42 (SD 14 ) years), 252 of their relatives (35 (17) years), 203 healthy controls (45 (16) years), and 92 patients with ischaemic heart disease (63 (11 ) years). Results - Abnormal antibody levels were commoner in patients with dilated cardiomyopathy (25, 20%) than in ischaemic heart disease (4, 4%), or normal controls (4, 2%, P = 0.001). Forty one (16%) of th e relatives had abnormal results compared to the controls (4, 2%, P < 0.001) and antibodies were detected in 20 (38%) of pedigrees. Relative s from non-familial kindreds had higher antibody levels than those wit h familial disease (P much less than 0.001), and higher antibody level s were identified in 53 relatives of probands who had abnormal results compared to 116 relatives for whom the proband had a normal result (0 .37 (SEM 0.02) v 0.22(0.01); P < 0.001). Conclusions - The finding of anti-alpha-myosin antibodies in 20% of patients with dilated cardiomyo pathy, in 16% of their asymptomatic relatives, and in 38% of families particularly those with nonfamilial disease and where proband also had an abnormal result) provides additional evidence for autoimmunity aga inst a myosin in a subset of patients.