Idiopathic calcification of the mitral valve.

The localization of primary calcified deposits in cases of idiopathic calcification of the mitralis was studied microscopically in the mitral tissue of 18 autopsy cases of women over 60. Macroscopic inspection revealed small calcified foci in 12 cases, none in the remaining 6. Microscopically, calcified foci were found in all cases, localized at the insertion of the mitral cusp. The annulus was involved in 8 cases only. At the site of cuspal insertion these foci were situated in fibrous thickenings towards the endothelial surface of the ventricularis. According to these findings, calcified deposits accumulate primarily at the cuspal insertion site, rather than in the annulus. Age-related fibrosis of the mitral cusp appears as a predisposing factor for dystrophic calcification.