A case of XYY Down's syndrome confirmed by autoradiography.

Double aneuploidy in Down's syndrome was first described by Ford et al (1959) in a patient showing both Down's and Kilnefelter's syndromes. Since then, at least 33 further cases of Down's syndrome have been described with additional aneuploidy (see Table). Approximately half of these are associated with autosomal aneuploidy, the remainder with abnormalities of the sex chromosomes among which are three definite examples of Down's syndrome with an additional Y chromosome. The first, a 9-year-old boy, was reported by Verresen and van den Berghe (1965); the second, a newborn infant, who died aged 7 weeks as a result of severe cardiac malformation, was reported by Uchida, Ray, and Duncan (1966). The third was men-