EVIDENCE FROM FAMILY STUDIES FOR AUTOIMMUNITY IN DILATED CARDIOMYOPATHY

Organ-specific antibodies are found in patients with autoimmune diseas e and their symptom-free relatives many years before clinical onset. O rgan-specific cardiac antibodies can be found in patients with dilated cardiomyopathy (DCM) and their relatives, which supports the idea tha t DCM is an autoimmune disease. We did non-invasive cardiological asse ssment and antibody screening in 342 symptom-free relatives (170 male, 172 female, mean [SD] age 31 [16] years). 177 relatives were from 33 families with more than 1 affected individual (familial DCM) and 165 r elatives from 31 families with only 1 affected member (non-familial DC M). The frequency of cardiac antibodies was higher among relatives of DCM patients than in controls (20% vs 3.5%, p = 0.0001). In 37 (58%) o f the families studied, cardiac antibodies were found in the proband a nd/or in at least 1 family member and were more common in familial tha n in non-familial DCM (24% vs 15%, p = 0.036). Antibody-positive relat ives were younger (26 [15] vs 33 [17] years, p = 0.01) and had a large r mean echocardiographic left ventricular end-systolic dimension (35 [ 6] vs 32 [6], p = 0.01 mm) and reduced percentage fractional shortenin g compared with antibody-negative relatives (31 [6] vs 34 [6], p = 0.0 08). Presence of cardiac-specific autoantibodies in symptom-free DCM r elatives provides evidence of autoimmunity in a subset of our patients (58%), including familial and nonfamilial forms of DCM. These antibod ies are associated with mild left ventricular systolic dysfunction on echocardiography and may be early markers for relatives at risk of DCM .