Chromosome mosaicism in a mentally retarded mother and her daughter.

Mosaicism for a chromosome of group G (21-22) has been described in many patients with typical Down's syndrome (Clarke, Edwards, and Smallpeice, 1961; Blank, Gemmell, Casey, and Lord, 1962; Smith, Therman, Patau, and Inhorn, 1962; Nichols, Coriell, Fabrizio, Bishop, and Bogg, 1962; Weinstein and Warkany, 1963; Lindsten, Alvin, Gustavson, and Fraccaro, 1962; Hayashi, Hsu, and Chao, 1962) and in some non-mongoloid people with varied clinical conditions (Biesele, Schmid, and Lawlis, 1962; Turner and Jennings, 1961; Fitzgerald, 1962; Dunn, Ford, Auersperg, and Miller, 1961; Zellweger, Mikamo, and Abbo, 1962; Sparkes, Veomett, and Wright, 1966). Familial transmission of an extra chromosome from one generation to the next is relatively rare, but has been detected in some cases in which a mosaic trisomy G-normal was found in the apparently normal parent of a mongol child (Smith et al., 1962; Blank et al., 1962; Weinstein and Warkany, 1963; Verresen, van den Berghe, and Creemers, 1964; Ferrier, 1964). However, repeated mosaicism in two generations is, to our knowledge, very infrequent. It is the purpose of this paper to report the occurrence of mosaicism in a mother and her 17year-old daughter. Both were mentally retarded but did not exhibit physical signs of mongolism.