Mitral valve prolapse (MVP [MIM 147700]) is among the most common cardiovascular abnormalities, affecting∼ 2%–8% of the population (Levy and Savage 1987). In fact, this abnormality is believed to affect as many as 15%–20% of young women and a significantly lower proportion (1%–3%) of men, suggesting to some clinicians that this abnormality is, in most cases, a trivial variant of normal valve architecture. However, since some adult patients ultimately require mitral valve replacement (Carpentier et al. 1980; Alpert et al. 1998) and since MVP is commonly associated with well-known clinical entities such as Marfan syndrome and Ehlers-Danlos syndrome (Glesby and Pyeritz 1989), others believe MVP to be a form of significant heart disease (Boudarias 1991).

MVP is described as excessive mitral valve tissue that leads to billowing of the mitral valve leaflets, with or without prolapse and mitral regurgitation (MR)(Frable 1969; Kern and Tucker 1972; Barlow and Pocock 1979; Virmani et al. 1987). Clinically, the diagnosis is suspected when a mid-systolic click and/or late-systolic cardiac murmur are auscultated (Barlow et al. 1963; Barlow and Pocock 1979; Perloff et al. 1986). The diagnosis is confirmed by echocardiography (Nishimura et al. 1985; Levine et al. 1988), and occasionally there is disparity in the physical exam findings and echocardiographic findings (Weiss et al. 1975). In some families, several affected individuals can be identified, with inheritance usually being autosomal dominant (Shappell et al. 1973; Weiss et al 1975; Bareiss 1976; Cooper and Abinader 1981; Strahan et al. 1983). Age dependence and sex dependence (Devereux et al. 1982) also have been noted. In addition, X-linked inheritance has been reported in a forme fruste of MVP, called “severe myxomatous valvular dystrophy,” which has been mapped to Xq28