46,XX,t (15;21) /47,XX,15p-,+21 mosaicism in a child with Down's syndrome
Lucas, J.; Le Mee, F.; Pluquailec, K.; Le Marec, B.; Journel, H.; Picard, F.
Annales de Genetique 29(2): 104-106
1986
ISSN/ISBN: 0003-3995 PMID: 2945509 Document Number: 270118
We report here the first case of a mosaic Down's syndrome in which both clones are trisomic for chromosome 21, one of them (90%) by a Robertsonian translocation (15;21) appearing de novo, and the other (10%) by an additional chromosome 21. Three hypotheses can explain the appearance of such a mosaic: that of a chimera formed by the fusion of two trisomy 21 zygotes, one of which had a Robertsonian translocation, the other an additional trisomy 21 zygote; that of a fusion between a chromosome 15 and a chromosome 21 in one of the early segmentation blastomeres of a trisomy 21 zygote; the more probable hypothesis of the occurrence of a fission at the break-attachment point of a Robertsonian translocation (15;21) in one of the cells arising from the early postzygotic divisions of a zygote which was a trisomy 21 by Robertsonian translocation (15;21).