Mitral valve (MV) prolapse (MVP) has a high prevalence of 2% to 3% in the general population and thus constitutes the most common cause of severe nonischemic MV regurgitation (MVR). MVP is also common in persons with the Marfan syndrome. However, to date, a large-scale population-based cohort study using modern echocardiographic techniques has not been performed, and the frequency of MVP and the relation of MV dysfunction and age have not been investigated. Therefore, we conducted a population-based cohort study of 204 patients (108 males and 96 females, aged 31.2 ± 16.4 years) with classic Marfan syndrome. We performed echocardiographic follow-up of 174 patients for a mean of 4.4 ± 4.3 years. On the initial or subsequent echocardiographic scan, MVP was present in 82 patients (40%), severe MVR in 25 (12%), and MV endocarditis in 5 patients (2.5%). At 30 years of age, the Weibull cumulative distribution was 42.6% (95% confidence interval [CI] 36% to 50%) for MVP, 56.5% (95% CI 49.3% to 64%) for MVR of any degree, 6.7% (95% CI 3.9% to 11.3%) for severe MVR, and 0.92% (95% CI 0.21% to 3.91%) for MV endocarditis. The cumulative hazard for severe MVR and MV endocarditis was estimated to increase with age. MVP was associated with dural ectasia (p = 0.01), ectopia lentis (p = 0.02), and skeletal involvement (p
