Frequency and phenotypes of familial dilated cardiomyopathy.

This prospective study was performed to analyze the frequency and clinical characteristics of idiopathic dilated cardiomyopathy (DCM). Despite several previous reports on families with DCM, most cases are still believed to be sporadic, and specific clinical findings of the familial form are not well defined. In 445 consecutive patients with angiographically proven DCM, we obtained detailed family histories to construct pedigrees and examined 970 first- and second-degree family members. Familial DCM was confirmed in 48 (10.8%) of the 445 index patients and was suspected in 108 (24.2%). The 156 patients with suspected or confirmed familial disease were younger at the time of diagnosis (p < 0.03) and more often revealed electrocardiographic changes (p = 0.0003) than patients with nonfamilial disease. Among the families of the 48 index patients with confirmed familial disease, five phenotypes of familial DCM could be identified: 1) DCM with muscular dystrophy; 2) juvenile DCM with a rapid progressive course in male relatives without muscular dystrophy; 3) DCM with segmental hypokinesia of the left ventricle; 4) DCM with conduction defects; and 5) DCM with sensorineural hearing loss. Up to 35% of patients with DCM may have an inherited disorder. Distinct clinical phenotypes can be observed in some families, suggesting a common molecular cause of the disease.