Increase of neutrophil alkaline phosphatase in the parents of trisomy 21 children. Hematological and cytogenetic studies.

A comparative study of karyotypes, hematological variables and neutrophil alkaline phosphatase (NAP) was performed in 106 parents (53 couples) of children with free, homogeneous trisomy 21 and of 220 parents (110 couples) of normal children. In the parents of trisomy 21 children we found a significant increase of the NAP (p <0.05) and a nonsignificant difference in the number of white blood cells. In 4 cases, we also found an anomaly in the karyotype. A modification of the metabolism of the neutrophils seems possible.