MYH6 in Congenital Heart Defects: A Genotype-Phenotype Characterization in a French Cohort.

Congenital heart defects (CHD) are among the most frequent congenital anomalies and represent a significant source of morbidity and mortality in infants. Both genetic and environmental factors are involved, and variants in the MYH6 are potential major genetic factors. The objective of the present study was to describe cardiac phenotypes in individuals with CHD and MYH6 variants. We included individuals with CHD and a MYH6 variant identified in four French genetics laboratories. Clinical and family data were collected. Of the 29 individuals included, 20 (68.9%) had a principal phenotype of left heart defect: hypoplastic left heart syndrome (n = 11, 37.9%), left heart obstruction at multiple sites (n = 6, 20.7%), and coarctation of aorta (n = 3, 10.3%). Nine individuals (31%) had other CHD, such as tetralogy of Fallot, pulmonary stenosis, and septal defects. Prevalence of persistent left superior vena cava (LSVC) was much higher here (n = 11, 37.9%) than in literature (0.31-5.9%). Most of the 19 MYH6 variants were heterozygous, missenses, and inherited. Family screening demonstrated incomplete penetrance and variable phenotypic expressivity. MYH6 variants are associated with various CHD with a predominance of left heart defects and persistent LSVC. Our findings support broad indication for the molecular screening of MYH6 in CHD-particularly when familial recurrence is uncertain.