Supravalvar aortic stenosis: discordance in monozygotic twins and reduction in severity of obstruction during childhood.

A monozygotic twin boy with supravalvar aortic stenosis had reduction in the degree of obstruction with body growth. His twin brother had normal cardiac anatomy. To our knowledge, this is the first report of improvement without intervention in a patient with supravalvar aortic stenosis and of discordance of supravalvar aortic stenosis in monozygotic twins.