Sex Chromosome DSD

Some DSD are caused by atypical combinations of sex chromosomes. Sex chromosome DSD, where there is aneuploidy, or lack of paired chromosomes, is the cause of Turner syndrome (45,X) and Klinefelter syndrome (47,XXY). In addition, there may be mosaic patterns of sex chromosomes, which include girls with Turner syndrome and Y-chromosomal cell lines, as well as patterns of asymmetrical sex development where a 45,X/46,XY pattern produces mixed gonadal dysgenesis and 46,XX/46,XY (and other variations) may cause ovo-testicular DSD. The presence of Y material in dysgenetic gonads is important to identify as this is associated with higher risk of germ cell tumours.