Because galactose-1-phosphate uridyl transferase has been reported to be elevated in the blood of patients with mongolism (21 trisomy), assay of this enzyme in the erythrocytes and leukocytes was performed in patients with the Philadelphia chromosome. Twenty normal individuals and 16 patients with the Ph1 chromosome were studied; 15 of the latter had chronic myelogenous leukemia and 1 had an unusual myeloproliferative disorder. The mean leukocyte enzyme level in the Ph1 group was not different from that in the normal group. The mean erythrocyte enzyme level in the Ph1 group was higher than that in the normal group; this difference might have been due to a younger population of red cells in the Ph1 patients.
To interpret the results, three postulates are presented. First, the relationship between chromosome 21 and this enzyme activity may be obscured by other controlling factors. Second, the long arm of this chromosome may play no role in transferase activity. Third, there may be no reduction of genetic material in a Ph1 karyotype.