Increased frequency of organ-specific cardiac antibodies in healthy relatives of patients with dilated cardiomyopathy: Evidence for autoimmunity in Polish families

Abstract

Background and hypothesis: Autoantibodies represent markers of autoimmune involvement and are found with increased frequency in patients and their symptom-free relatives at risk compared with normal controls. Cardiac- specific autoantibodies, detected by immunofluorescence, were found in 20% of symptom-free relatives of patients with dilated cardiomyopathy (DCM) from England and Italy. The role of autoimmunity may vary in DCM patients from Poland due to ethnic differences in genetic susceptibility to autoimmune disease. Methods: We assessed the frequency of the organ-specific cardiac autoantibodies in 162 symptom-free relatives of DCM patients [85 male, mean (SD) age 27 (18) years] and 80 control subjects from Poland. Familial DCM (> 1 affected member) was present in 4 families, nonfamilial DCM in the remaining 24 pedigrees. We performed antibody screening and noninvasive cardiological assessment in the whole group. Results: The frequency of cardiac-specific autoantibodies was higher among patients with documented DCM (probands and relatives) (50%) and their symptom-free relatives (38%) than in unrelated normal subjects (10%; p=0.0001). In 24 (86%) of the pedigrees studied, autoantibodies were found in the proband and/or in at least one family member and tended to be more common in familial than in nonfamilial DCM (50 vs. 35%, p=NS). Echocardiographic indices of left ventricular size and function were similar in relatives with and without detectable antibodies. Conclusions: The presence of cardiac-specific autoantibodies in symptom-free relatives of DCM patients provides evidence for autoimmunity in the majority (86%) of our pedigrees, including both familial and nonfamilial forms of DCM.