Clonal origin of cells restricted to monocytic differentiation in acute nonlymphocytic leukemia.

Two patients with acute monocytic leukemia and heterozygous for the Mediterranean variant of the X-linked enzyme, glucose-6-phosphate dehydrogenase (G6PD), were investigated to determine the number and type of progenitor cells involved. Mosaicism for Mediterranean G6PD was assessed by the different rate of utilization of 2-deoxy glucose-6-phosphate (2dG6P) by normal and Mediterranean variants of G6PD. The monocytoid blasts were found to express one type of G6PD only, indicating their clonal origin from a common progenitor cell, whereas all other hemopoietic cell populations tested expressed the heterozygous phenotype. The finding of a unique involvement of the monocytic line in two cases of acute nonlymphocytic leukemia (ANLL) represents further evidence of heterogeneity of stem cell involvement in ANLL.