Inheritance of the mitral valve prolapse syndrome. Discussion of a three-dimensional penetrance model

The families of 12 probands with classic mural valve prolapse were studied for evidence of mitral valve prolapse. Seventy parents, sibs, and progeny were included in the analysis. Forty-seven percent (16 of 34) of progeny were affected compared with 30 percent (3 of 10) of parents. Thirty-eight percent (10 of 26) of sibs were affected. A three-compartmental penetrance model was devised to account for the variation in expression with age. This includes a latent stage (time before onset of signs), an affected stage, and a stage in which the subjects are withdrawn (because of treatment, regression, or death). The implications of this model are discussed.