Cytogenetic studies in children with Down syndrome and acute leukemia.

The frequency of chromosomal alterations was compared among four children groups: those with Down syndrome and acute leukemia (DS/AL), those with acute leukemia (AL), those with only Down syndrome (DS) and healthy children (NC). The frequency of acquired chromosome abnormalities was larger in the AL group, followed by the DS/AL. The gaps and isogaps were more frequent in children with only DS. The polymorphisms of the constitutive heterochromatin were larger in the DS/AL group. These findings appear to imply that more genetic changes are necessary to develop AL in the case of healthy children compared to children with DS.