[Turner syndrome and mosaicism]

Turner's syndrome is a gonadosomatic dysgenesis of female phenotype due to a more or less complete monosomy of one of the X chromosomes leading to a haploinsufficiency of the development genes situated at the level of the pseudoautosomal region of the gonosomes. Further experience of the karyotype showed a preponderance of mosaics and considerable variability of Turner's phenotype in proportion to the number of 45, X cells. The rare cases of monozygotism discordant with variable tissular distribution mosaics show that the phenotypic expression is a genic dosage effect. In patients with TS it would thus be of interest to study a second tissue such skin fibroblasts when a discordance is observed between the phenotype and the karyotype.