Chromosome damage in Down's syndrome induced by chickenpox infection.

Chromosomes were studied in 74-hr lymphocyte cultures from seven patients with Down's syndrome and from 12 hematologically and karyotypically normal control subjects. Six were studied before and six after chickenpox infection. In Down's syndrome, the number of breaks per cell was 0.083 +/- 0.036 immediately after chickenpox infection; this was significantly greater than the number of breaks before infection, 0.03 +/- 0.008, and also significantly greater than the number of breaks, 0.046 +/- 0.023, observed in control children with chickenpox. Therefore, chromosomes from patients with Down's syndrome were significantly more sensitive to breakage after chickenpox infection than those from control subjects. The incidence of chromosome breaks in Down's syndrome 1 month after chickenpox infection fell to the level observed in the preinfection range. The present results showed that the difference between the observed and the expected values for breakage in special regions of chromosome was not significant, but that chromosome breakage was random.