Williams syndrome (WS) is a multisystem developmental disorder caused by deletion of 26-28 genes, including the elastin gene, located on chromosome 7q11.23. Cardiovascular disease in WS, including obstructive vascular disease and hypertension, and relatively mild skin changes are caused by the elastin gene deletion. Even though all WS subjects are missing one copy of this gene, the expression of cardiovascular problems is highly variable, ranging from no significant disease to severe generalized arteriopathy leading to infant death. The causes of vascular variability are currently unknown, and male gender is the only disease modifier described to date. Clinically, skin is described as abnormally soft, smooth and easily mobilized , while ultrastructurally the elastic fibers are abnormal with reduced amorphous elastin.