There are multiple dysmorphic features. Most cases, as in Down's syndrome, involve maternal non-disjunction. Again, a significant fraction have a parent who is a translocation carrier. Again most babies die in the first year and many within the first month. Because of X inactivation and because of the paucity of genes on the Y chromosome, aneuploidies involving the sex chromosomes are far more common than those involving autosomes.
Individuals are very short, they are usually infertile.
Characteristic body shape changes include a broad chest with widely spaced nipples and may include a webbed neck. IQ and lifespan are unaffected. The incidence at birth is about 1 in 1000 males. There is no spermatogenesis. These individuals are generally severely retarded.