MAPPING OF X-LINKED MYXOMATOUS VALVULAR DYSTROPHY TO CHROMOSOME XQ28

Myxoid heart disease is frequently encountered in the general populati on. It corresponds to an etiologically heterogeneous group of diseases , idiopathic mitral valve prolapse (IMVP) being the most common form. A rarely observed form of myxoid heart disease, X-linked myxomatous va lvular dystrophy (XMVD), is inherited in an X-linked fashion and is ch aracterized by multivalvular myxomatous degeneration; however, the his topathological features of the mitral valve do not differ significantl y from the severe form of IMVP. In this article, we describe the genet ic analysis of a large family in which XMVD is associated with a mild hemophilia A. The coagulation factor Vm gene position in Xq28 provided a starting point for the genetic study, which was conducted by use of polymorphic markers. Two-point linkage analysis confirmed this locali zation, and a maximum LOD score of 6.57 was found at theta = 0 for two polymorphic microsatellite markers, INT-3 and DXS1008, the first one being intronic to the factor Vm gene. Haplotype analysis of this chrom osomal region allowed the definition of an 8-cM minimal interval conta ining the gene for XMVD, between DXS8011 and Xqter.