The most common cause of death in patients in Marfan syndrome patients is

Between 75% and 85% of patients with the Marfan syndrome have dilatation of the ascending aoa and annuloaoic ectasia (dilatation of the aoic sinuses and annulus). Such aoic abnormalities are the most common cause of death among patients with Marfan syndrome ref - Harrisons 20edition pg1918,2975,829