[45,X/46,X,del(Yq) sex chromosome mosaicism--analysis of the phenotypic expression].

Three female patients with Turner-syndrome (sexual infantilism, short stature and somatic Turner-stigmata) have been analysed cytogenetically by means of different banding techniques. A deletion of the distal heterochromatic band Yq12 of the Y chromosome was observed in a mosaic with a 45,X-cell line, i.e. the karyotype is 45,X/46,X,del(Y)(q12). In order to get information about the phenotypic expression of the 45,X/46,X,del(Yq) mosaicism all previously published cases have been reviewed. Comparing the phenotypes of all 45,X/46,X,del(Yq) mosaic cases three different phenotype categories of sexual development can be distinguished: female individuals with sexual infantilism and Turner-stigmata, individuals with ambiguous genitals, ranging from clitoris hypertrophy of female genitals to hypospadia of males, male individuals, who are infertile (azoospermic). A comparison of the appearance of external genitals with the status of gonads of all patients revealed an unequivocal relationship between the gonad status and the resulting phenotype category. Furthermore, the role of Y-chromosomal loci determining testicular differentiation (biological function of H-Y antigen) for male development has been emphasized. The effect of the 45,X-cell line on the expression of short stature and somatic Turner-stigmata is independent of sexual development. Considering the great phenotypic variability of the 45,X/46,X,del(Yq) mosaicism it seems impossible to deduce a definitive phenotype. This problem is acute in prenatal diagnosis especially.