Down's syndrome. I. Cytogenetics.

A number of 107 children with clinical diagnosis of Down's syndrome have been studied. In 80% of the cases the parents have been cytogenetically investigated, too. Of these, 82.2% (88 cases) had free trisomy, 9.4% (10) had 46/47 + 21,4.7% (5 cases) had 14/21 translocation, 1 case (0.3%) had 21/21 translocation, one case translocation in inverse tandem, one case had iosochromosome 21, one case had 48.XXY + 21. These observations may be of help in establishing the prophylaxis of the syndrome, i.e.; 1. Cytogenetic investigation of all children suspect of having Down's syndrome, and in the case of translocation, of their parents as well. In the case of hereditary translocations it is recommended that the whole kinship be studied; 2. Monitoring of pregnancies of mothers over the age of 35 seems necessary.