Cell selection in vivo. Follow-up of nine unselected mixoploid children.

A cytogenetic follow-up has been made of nine mixoploid children found among 11 148 consecutive newborn children. The frequency of the cell line with normal chromosomes increased in all but two, and the increase was statistically significant, being from 20% to 39% in four cases, and from 1% to 17% in three, while in one case there was no difference from the first to the last examination. The possibility that children with mixoploid chromosome abnormalities at birth will reveal no cell line with a chromosome abnormality in lymphocyte cultures as adults, despite having clinical signs of the chromosome aberration found in one cell line at birth is discussed, as is the question of cell selection in vivo. The mixoploid children had fewer clinical symptoms and fewer signs of the chromosome abnormalities found in some of their cells than children with the same chromosome abnormalities in all cells.