Sex chromosome aneuploidy in fragile X carriers.

Not few reports of sex chromosome aneuploidy in association with the fragile site at Xq28 have appeared, suggesting other factors than pure coincidence. In the present report lymphocyte cultures from 23 obligate and 45 potential carriers have been examined cytogenetically. As expected, an increase in sex chromosome aneuploidy with increasing age was observed. However, it seemed that the increase of hyperdiploid cells was far in excess of the expected, and a difference between obligate and potential carriers was apparently also present. Hence, a disposition to non-disjunction of the fragile X chromosome is suggested.