TRISOMY X OR Y MOSAICISM(47,XXX, 47,XXY, 47,XYY)
Non-mosaic aneuploidy at CVS has been confirmed in fatal tissues in still quite small numbers with follow-up. Information on the outcome of mosaic CVS cases is sparse , particularly for 47, XYY mosaicism. For 47, XXX mosaicism, 2/4 cases were confirmed in fetal tissues. 1/3 cases of 47 XXY mosaicism at CVS proved to be genuine. (Smith et al, 1999)
Sachs et. al. (1990) reported on 2 cases of sex chromosome mosaicism which were mosaic for normal male cells, 46,XY and aneuploid cells, 47,XXY. In these cases the percentage of abnormal cells measured on CVS direct studies were 55% and 94%. Both pregnancies were terminated. In one mosaicism was confirmed, in the other trisomic cells did not appear to be in the fetus.
Uniparental Disomy (UPD)
Link to What is UPD?
Link to Maternal UPD X
Link to Paternal UPD X
No cases reported for UPD Y
Confined Placental Mosaicism (CPM)
Sex chromosome abnormalities restricted to the placenta have not been closely associated with an adverse pregnancy outcome (Wolstenhome et. al, 1994).
Ledbetter DH, Engel E. (1995) Uniparental disomy in humans: development of an imprinting map and its implications for prenatal diagnosis. Human Molecular Genetics 4:1757-1764 PubMed
Sachs ES, Jahoda MG, Los FJ, Pijpers L, Reuss A, Wladimiroff JW. (1990) Interpretation of chromosome mosaicism and discrepancies in chorionic villi studies. American Journal of Medical Genetics 37:268-71. PubMed
Smith K, Lowther G, Maher E, Hourihan T, Wilkinson T, Wolstenholme J. The predictive value of findings of the common aneuploidies, trisomies 13, 18 and 21, and numerical sex chromosome abnormalities at CVS: experience from the ACC U.K. Collaborative Study. Association of Clinical Cytogeneticists Prenatal Diagnosis Working Party. Prenat Diagn. 1999 Sep;19(9):817-26. PubMed