Mutations in Hotspot Region of MYH7 Gene Exon 23 Associated with Restrictive Cardiomyopathy

Restrictive cardiomyopathy (RCM) is characterized by restrictive filling of the ventricles. The association between the variable expressivity and age at onset of disease and disease complexity with double and compound heterozygous state is associated with severity of disease phenotype in recent reports. Sharing of variants of sarcomere genes across cardiomyopathies has implication in clinical expression of different clinical phenotypes. The present study reports Sanger DNA sequencing of MYH7 gene, exon 23 from 30 unrelated RCM patients and 15 primary relatives from sporadic families with the hypothesis that RCM has common etiology with hypertrophic cardiomyopathy (HCM). Rare variant E949K and a de novo compound heterozygous mutation (p.E902K and p.D906N), in two RCM patients with early onset and no ventricular hypertrophy were found. These variants wereabsent in 50 dilated cardiomyopathy, 50 HCM patients and 15 primary relatives screened. The present report of rare and compound heterozygosity cases will further provide basis for the complexity and variable expressivity of phenotypes in patients in such complex diseases. The possible reasons for this phenotypic heterogeneity would be the presence of any other mutations in same chromosome or in different chromosome which is modifying the outcome of the causal mutation.