New phenotype of familial dilated cardiomyopathy and conduction disorders

Background Familial dilated cardiomyopathy (FDCM) is attributed to defects in cytoskeletal proteins, and different patterns of inheritance and phenotypic expressions according to assorted-protein modifications have been identified to date. We describe a clinical family study with 24 individuals in 3 generations affected by dilated cardiomyopathy (DCM) and cardiac conduction abnormalities. Methods and Results After a follow-up period of 25 ± 14 months, DCM developed in 7 male adults, 6 with associated arterioventricular block (AVB); and 10 female and 7 male adults had several degrees of isolated AVB. This particular clinical expression, with a strong predominance of dilation of the heart developing in the male population and the vertical distribution of patients affected with AVB, is consistent with autosomal dominant inheritance involving both cardiac abnormalities. Conclusions The presence of isolated AVB or that associated with DCM in a large number of individuals in the same family, in which members of the male sex seems to be predominantly affected by cardiac dilatation, differs from other FDCMs that have been described previously. This FDCM has an autosomal dominant pattern of inheritance with variable phenotypic expressivity, in which AVB may constitute in itself the only manifestation of this entity. To date, we have been unable to identify the mechanism of inheritance, and we advance some theoretical considerations about possible mechanisms. (Am Heart J 2003;145:317-32.)