Duplication of the mitral valve.

Duplication of the mitral valve is a rare congenital cardiac anomaly, only twenty instances having been previously reported. There are on record in addition two cases of triplication of the mitral valve, a condition presumably resulting from a similar defect in development. Duplication of the tricuspid valve also occurs, but less commonly than the mitral anomaly. This case is reported in order to draw attention to several interesting facets of the condition, namely, the embryology, the occasional presence of an apical diastolic murmur, and the association with certain other congenital cardiac anomalies.