Leukocyte alkaline phosphatase was measured by a biochemical method in a group of 58 mongolian idiots. The mean activity found in the 41 children less than 10 years of age was equivalent to 89 mg. of phosphorus per 1010 neutrophilic leukocytes per hour. This was compared to the value of 66 mg. of phosphorus per 1010 neutrophilic leukocytes per hour obtained in a group of 41 control children in the same age group (after correction of the control mean to the same mean age). The difference is significant at the 0.5 per cent level of confidence.

This difference was interpreted as confirming (but not proving) the hypothesis that leukocyte alkaline phosphatase formation is controlled by a gene on chromosome number 21—the chromosome for which mongolian idiots are trisomic. The hypothesis arose because of the known deficiency of this enzyme in the leukocytes of patients with chronic granulocytic leukemia, and the known partial deletion of chromosome 21 in this disease.

This finding should provide a stimulus to further investigations into the content of alkaline phosphatase in leukocytes, possible polymorphism of leukocyte alkaline phosphatases, linkages with other inherited traits, and relationships between leukocyte and other tissue phosphatases.

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© 1963 by American Society of Hematology, Inc.
1963
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