Cell selection in vivo in normal/aneuploid chromosome abnormalities

Cytogenetic follow-up examination has been made of the 9 mixoploid children found among 11 148 newborn children. In 4 of the 9 children there was a significant increase in the frequency of the cell line with normal chromosome constitution and a significant decrease in the normal cell line was found in 1 child. In 4 there was no significant difference from the first to the last examination. The frequency of the cell line with normal chromosomes increased from 32-68% to between 93-97% in 3 cases and to 86% in 1. The possibility that children with mixoploid chromosome abnormalities at birth will reveal no cell line with chromosome abnormality in lymphocyte cultures as adults in spite of having clinical signs of the chromosome aberration found in one cell line at birth is discussed.