1/2. Re-analysis by fluorescence in situ hybridisation of spare embryos cultured until Day 5 after preimplantation genetic diagnosis for a 47, XYY infertile patient demonstrates a high incidence of diploid mosaic embryos: a case report.mosaicism in 4-8-cell human embryos analysed by fluorescence in situ hybridisation (FISH) has been widely reported, but few studies have addressed the incidence of mosaicism in more advanced embryonic stages. In the present study we analysed spare human embryos in a case of preimplantation genetic diagnosis (PGD) for increased risk of aneuploidy because of an infertile 47,XYY man. After replacement of two embryos typed as 1818XX at PGD, six spare embryos (not frozen because of their low quality) were re-analysed on Day 5 for PGD confirmation. Out of five embryos typed as 1818XY at PGD, four were diploid mosaic (DM) and one was normal in all cells. The sixth embryo, typed as 18XYY/1818181818X at PGD, was a DM. In spite of the bias of our small series of morphologically low-quality embryos, the surprisingly high proportion of mosaics (which confirms previous findings) questions the validity of PGD, but supports the strategy of transferring only the embryos where two blastomeres gave normal and concordant results at PGD. More data are required to understand the clinical significance of early diploid mosaicism (and its impact on implantation rate) and to determine whether some diploid mosaic embryos might be considered safe for transfer.- - - - - - - - - - ranking = 1keywords = embryo (Clic here for more details about this article) |
2/2. Discrepancy in mosaic findings between chorionic villi and amniocytes: a diagnostic dilemma involving 45,X, 46,XY, and 47,XYY cell lines.Discrepancies between cytogenetic findings in chorionic villi (CV) and fetal tissue have been reported. Several embryogenic models have been proposed to explain such discrepancies. We describe a case in which analysis of the direct preparation showed 24% 45,X and 76% 46,XY, with 43% 45,X and 57% 46,XY cells in cultured villi. amniocentesis results disclosed 97% 46,XY and 3% 47,XYY. No 45,X cells were found in cultured amniocytes. These findings suggest that nondisjunction occurred early in postzygotic cleavage resulting in 3 cell lines. It is postulated that through selection, the less viable 45,X cells died out among those destined to become fetus proper but persisted among the cytotrophoblast and extraembryonic mesoderm cells. While there is probably selection against all aneuploid cell lines, 47,XYY cells are more likely to survive in the fetus. An explanation for the lack of 47,XYY cells in the CV might be simply that the tissue sampled was not representative of the cytogenetic make up of the entire placenta.- - - - - - - - - - ranking = 0.11111111111111keywords = embryo (Clic here for more details about this article) |