The most fatal complication of Marfan syndrome is cardiovascular complications, which include aortic aneurysm and aortic coarctation. The majority of patients have progressive dilatation of the aorta resulting in incomplete closure of the aortic valve, followed by a coarctation aneurysm caused by degeneration of the middle layer of the aorta; rupture of this aneurysm is the main cause of premature death.