Hypertrophic cardiomyopathy due to beta-myosin heavy chain mutation with extreme phenotypic variability within a family

Hypertrophic cardiomyopathy (HCM) affects 1 in 500 persons and shows high variability in severity of disease, in genetic heterogeneity and phenotypic patterns. Many affected individuals remain undetected throughout their lives. In this case report a family with proven beta-myosin heavy chain mutation (MYH7) with 3 affected family members with huge phenotypic variability is described. The index patient (male, age 21 years) has severe phenotypic expression with a pathological ECG and maximal septal wall thickness of 29 mm, there is no significant obstruction in the left ventricular outflow tract. The sister (age 16 years), mutation carrier, has no detectable hypertrophy and no ECG changes. The mother (age 44 years), also carrying the mutation, has a normal ECG and shows only mild septal hypertrophy of 12 mm and systolic anterior motion of her mitral valve chordae with no gradient. The maternal grandmother died suddenly at age 65 years of presumed coronary artery disease, and the maternal great-grandmother had a sudden cardiac death at age 50 years of unknown etiology. To conclude, this family shows impressively the wide spectrum of phenotypic presentation and outcome in one family.