The syndrome of prolapse of the mitral valve: an etiologic and pathogenic enigma.

Prolapse of the mitral valve has superseded rheumatic heart disease in recent years as the most common cause of isolated mitral insufficiency in Europe and North America. This condition is recognized with increasing frequency, and its prevalence increases with age, apparently afflicting more than 5% of all persons older than 50 years of age. Consequently, mitral valve prolapse has acquired considerable medical and economic importance. Familial and nonfamilial forms are recognized. Nonfamilial forms can be further classified into cases that occur in statistically significant association with other diseases, and sporadic cases that include those possibly secondary to other conditions.