Genetic aspects of supravalvular aortic stenosis.

Supravalvular aortic stenosis (SVAS) occurs as an autosomal dominant trait or as part of the phenotype of the usually sporadic condition Williams syndrome. SVAS is the result of mutation or deletion of the elastin gene (ELN), located at chromosome 7q11.23. Thus, SVAS may be more appropriately termed an elastin arteriopathy. Studies have demonstrated various point mutations and intragenic deletions of ELN resulting in nonsyndromic SVAS. Individuals with Williams syndrome are hemizygous for the elastin gene, owing to a 1 to 2 megabase deletion of a portion of the long arm of chromosome 7 that encompasses ELN. This submicroscopic deletion is readily detected by fluorescent in-situ hybridization, useful in the diagnosis of Williams syndrome. The severity of SVAS is quite variable, both in series of Williams syndrome patients and within SVAS kindreds, suggesting that other genetic factors are involved in expression of the phenotype. Experiments with elastin knockout mice will likely yield clues regarding the role of elastin in arterial morphogenesis and the pathogenesis of obstructive vascular disease.