What is the familial prevalence and genetic transmission pattern of idiopathic hypertrophic subaortic stenosis?
Idiopathic hypertrophic subaortic stenosis (hypertrophic cardiomyopathy) is transmitted as an autosomal dominant trait with high penetrance, and echocardiography is essential for family screening as clinical and ECG findings are often absent.
The pattern of inheritance of asymmetric septal hypertrophy, the characteristic anatomic abnormality in idiopathic hypertrophic subaortic stenosis, was studied by echocardiography in 30 families, in 28 of which at least one first-degree relative of the proband also had asymmetric septal hypertrophy. Forty-six per cent of 105 first-degree relatives studied had the disorder; an equal percentage of males and females were affected. Penetrance was complete in nine of the 10 parental pairs available for analysis. Clinical features were unreliable for detection of asymmetric septal hypertrophy since only 16 per cent had findings of classic idiopathic hypertrophic subaortic stenosis. The history was negative in 60 per cent, and the physical examination in 65 per cent. The electrocardiogram was normal in 50 per cent of those with asymmetric septal hypertrophy on echocardiography. Most cases of the disorder appear to be due to a genetic defect that is transmitted as an autosomal dominant trait with a high degree of penetrance. (N Engl J Med 289:709–714, 1973)
Clark et al. (Thu,) studied this question.
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