Genetics

Supravalvular aortic stenosis is inherited in an autosomal dominant trait:

• it has been shown that SVAS may be caused by a chromosome translocation which disrupts the elastin gene (1)

William's syndrome is usually sporadic

• some patients with William's syndrome are hemizygous for (only have one copy of) the elastin gene, on chromosome 7
  • syndrome occurs due to a deletion spanning 1,500 kb at the q11.23 region of human chromosome 7
    • the specific architecture of this region predisposes it to unequal recombination
      • the deletion covers about 20 genes; the hemizygosity of these genes has multiple effects: a specific, 'elfin' facial appearance, developmental disorders, a variety of cardiovascular diseases, neurological abnormalities and cognitive features, hypersocialisation, and musical talent (2)

Reference:

• Ewart, AK. et al. (1993). Hemizygosity at the elastin locus in a developmental disorder, Williams syndrome. Nature Genet. 5, 11-6.
• Pober B.R., Johnson M., Urban Z.. J. Clin. Invest. 2008;118(5):1606-1615