An XO-X ring X chromosome mosaicism in an individual with normal secondary sexual development.

Ring chromosomes in man, in association with congenital abnormalities, have been reported involving a chromosome in the I7-I8 group (Genest, Leclerc, and Auger, I963; Gropp, Jussen, and Ofteringer, I964; Lucas, Kemp, Ellis, and Marshall, I963; Wang, Melnyk, McDonald, Uchida, Carr, and Goldberg, I962), a chromosome in the X-6-I2 group which is probably not an X (Turner, I963), a member of the I3-15 group (Smith-White, Peacock, Turner, and Den Dulk, I963), a No. i chromosome (Gordon and Cooke, I964), and on five occasions an X chromosome (Bain, Gauld, and Farquhar, I965; Hustinx and Stoelinga, I964; Lindsten and Tillenger, I962; Luers, Struck, and Nevinny-Stickel, I963; Pfeiffer and Biichner, I964). We report the findings in a further patient with a presumptive ring X chromosome.