Chromosome Mosaicism in an Indian Child with Down's Syndrome.

Since the first report by Lejeune, Gautier, and Turpin in 1959 of the findings of trisomy 2I and a chromosome number of 47 in Down's syndrome (mongolism), several different chromosomal patterns have been described in patients with this disorder. One of these is chromosome mosaicism. In such cases, the patient may lack some of the features characteristic of the syndrome-and indeed some subjects with mosaicism are hardly distinguishable phenotypically from normal people (Fraccaro, Kaijser, and Lindsten, I960; Hamerton, Briggs, Giannelli, and Carter, I96I; Blank Gemmell, Casey, and Lord, I962; Smith, Therman, Patau, and Inhorn, I962; Tonomura, Honda, and Kurita, I962; Weinstein and Warkany, I963). Several cases of mosaicism in Down's syndrome are now on record and 24 are listed in Table I: i6 possess two types of cells containing 46 and 47 chromosomes respectively, i.e. are mosaics of normal and 2I trisomic cells (Aula, Hjelt, and Kauhtio, I96I; Clarke, Edwards, and Smallpeice, I96I; Hayashi, Hsu, and Chao, I962; Lindsten, Alvin, Gustavson, and Fraccarro, I962; Nichols, Coriell, Fabrizio, Bishop, and Boggs, I962; Richards and Stewart, I962; Giraud, Bernard, Stahl, Giraud, Hartung, and Lebeuf, I963; Hayashi, I963; Verresen, Van Den Berghe, and Van Den Berghe, I963; Zellweger and Abbo, I963; Gustavson, I964; Stearns, Droulard, and Sahhar, I960; Warkany, Weinstein, Soukup, Rubinstein and Curless, I964; Zellweger and Abbo, I964); 2 have also two cell types but carry a possible isochromosome for the long arm of No. 21 (iSo-1-2I) (Hamerton et al., I96I; Blank, Lord, Casey, and Laurance, I963); 3 show triple cell lines with 46, 47, and 48 chromosomes, 2 of them with a probable isochromosome (Fitzgerald and Lycette, I96I; Gustavson and Ek, I96I; Gustavson, 1964; Mauer and Noe, I964). One, reported by Valencia, de Lozzio, and de Coriat (I963), has several cell lines with