[Clinical characteristics of the mosaic variant of Down's disease].

The authors studied the clinical features in 19 patients with the mosaic variety of Down's disease and 63 patients with trisomia in relation to the 21st chromosome. It was demonstrated that mild forms of mental retardation are mainly seen in mosaicism rather than in the trisome variety, although severe forms of retardation may be seen in the first group as well. A full correlation between the severity of mental retardation and the % of the aneuploid cell content in the peripheral blood was not always observed.