Dystrophic aortic regurgitation is the result of 2 diseases: (1) aortic regurgitation, consequence of (2) aortic dilatation due to decreased aortic wall resistance. Marfan syndrome, which is a genetic disease, should be looked for systematically, with the help of an ophthalmologist and a rheumatologist. Aortic dilation is responsible for the increased mortality because of aortic dissection. Diagnosis is often made when the aorta is dilated wheras the aortic regurgitation is minimal or moderate; when the patient is asymptomatic. This has 2 consequences: siblings of Marfan patient should be examined by echocardiography; surgical replacement of the ascending aorta is often performed because of the aortic dilation, not because of the aortic regurgitation.