Cardiocytolytic antimyolemmal antibodies in dilated cardiomyopathy following presentation: observations in 7 patients.

The prevalence of lytic activity of circulating antimyolemmal antibodies in dilated cardiomyopathy of recent onset is unclear. To obtain preliminary data we studied 7 consecutive patients with dilated cardiomyopathy (age 44 +/- 14 years) and symptoms for fewer than 6 months. The presence of antimyolemmal antibodies was determined in vitro using intact rat and human cardiocytes and indirect immunofluorescence. Serum cytolytic index for antimyolemmal antibodies was measured by microcytotoxicity assay and the data were compared with that from 70 controls (normal range 0.92 +/- 0.07, effective cytolysis < 0.75). Autoantibody screening was uniformly negative and only 1 patient had positive viral serology. Light microscopy of cardiac biopsies revealed non-specific histology in 2, focal myocarditis in 1 and healing or healed myocarditis in 4. Significant binding of IgG, IgM or polyvalent antibodies to antimyolemmal antibodies bound to rat or human cardiocytes was present in every patient and 5 of them were positive with all 3 markers. Cytolytic index for the group ranged from 0.47 to 0.60 indicating effective lysis in all patients (P < 0.01 versus controls). Cardiocytolytic antimyolemmal antibodies are commonly present in dilated cardiomyopathy following presentation. Their detection might reflect ongoing disease activity and help identify patients likely to benefit from immunomodulative therapy.