Supravalvular aortic stenosis is associated with the Williams-Beuren syndrome, but it also occurs in a non-syndromatic congenital form. An elastin gene mutation of chromosome 7q11.23 is responsible in both cases. The vascular features are identical. These patients have a higher risk of sudden death, particularly when undergoing diagnostic or surgical procedures. We report the account of a family with a new mutation in the elastin gene. Screening over three generations revealed eight affected individuals. The cardiac and vascular malformations ranged from mild asymptomatic supravalvular aortic stenosis and isolated dysplastic atrioventricular valves to diffuse arterial hypoplasia. Two infants presented arteries affected at multiple locations, including the left coronary artery. Both died of sudden cardiac death and myocardial ischaemia, one while under general anaesthesia for cardiac catheterisation, and the other perioperatively. We discuss the pathophysiological aspects in these patients that deserve consideration before any general anaesthesia is administered.