Background: There is increasing awareness of the familial nature of dilated cardiomyopathy (DCM). Mutations in the genes coding for cytoskeletal and sarcomere proteins have been identified. Phenotyping of familial DCM (FDCM) may help to improve genetic diagnosis. The aim of our study was to evaluate the clinical features, pattern of transmission, and immunogenetic data of FDCM.
Material/Methods: We obtained family histories in order to construct pedigrees and prospectively evaluated 204 family members of 27 patients with angiographically proven DCM. FDCM was defined as
more than 1 person with DCM in a family. The study protocol included repeated clinical examination, electrocardiography, echocardiography and blood sampling.
Results: Among the families, we identified the following phenotypes: DCM with conduction defects (n=2), early onset DCM with a rapid course in male relatives (n=2), and DCM preceded by ventricular arrhythmia (n=1). The remaining families presented with a heterogeneous course of the disease. The disease was transmitted in an autosomal dominant fashion in 14 of our pedigrees, possibly X-linked in three and indeterminate in 10 sib-pairs. The frequency of the
DRB1*04 allele was low in probands with the disease (3/20, 15%); heterozygozity for DRB1*03/DRB1*04, known to increase susceptibility to IDDM1, was identified in 2 of 20 DCM probands (10%).
Conclusion: Familial dilated cardiomyopathy is a heterogeneous disorder; autosomal dominant transmission is most common. The distinct clinical phenotypes and specific immunogenetic features
found in some families indicate that different pathogenetic mechanisms can lead to the disease.

Keywords: Adolescent, Alleles, Arrhythmia - genetics, Arrhythmia - immunology, Arrhythmia - physiopathology, Cardiomyopathy, Dilated - genetics, Cardiomyopathy, Dilated - immunology, Cardiomyopathy, Dilated - physiopathology, Child, Chromosomes, Human, X - genetics, Gene Frequency, Genes, Dominant, HLA-DR Antigens - genetics, Immunogenetics, Linkage (Genetics), Pedigree, Phenotype, Prospective Studies