Genetic analysis of mosaicism in 53 women with Turner syndrome

Mosaicism involving the sex chromosomes is a common finding in women with T urner syndrome (TS). It is especially important to detect Y-chromosomal mat erial, since this is a risk factor for the development of gonadoblastoma. R ecent studies have also indicated that the frequency of 45,X cells may be u sed to predict prognosis. As part of an ongoing multi-disciplinary study, w e have examined the extent of Y-chromosomal material and sex chromosomal mo saicism and its tissue specificity in 53 women with TS. The results of lymp hocyte karyotyping were compared with the use of interphase X/Y fluorescenc e in situ hybridisation (FISH) analysis of lymphocytes and buccal mucosal c ells. As could be expected, an extended FISH analysis detected more Y-chrom osomal material than karyotyping (in 15 % vs. 11 % of the women, respective ly) and also detected more X-chromosomal mosaicism among the TS women (in 7 0 % vs. 45 % of the women, respectively). In half of the women, tissue-spec ific differences between lymphocytes and buccal mucosal cells were found. B ased on these results, we suggest the use of X/Y interphase FISH as a compl ement to karyotyping in order to obtain a more complete knowledge of the ch romosome constitution of each individual with TS.