Why is glucose-6-phosphate dehydrogenase deficiency more fully expressed in many males than females?

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blood disease Peripheral blood smear revealing histopathologic features indicative of a blast crisis in a case of chronic myelogenous leukemia (CML). Blast crisis occurs when one-fifth to one-third of the cells in the blood or bone marrow are immature blood cells, or blast cells. This phase of CML is characterized by fever, weakness, and an enlarged spleen.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a hereditary metabolic disorder that is considered a sex-linked condition, which explains why it is more fully expressed in males than in females.1

The gene responsible for producing the G6PD enzyme is located on the X chromosome. Because males possess only one X chromosome, they have no second copy of the gene to compensate if the one they carry is defective. In contrast, females possess two X chromosomes; if one carries the mutation, the other typically provides enough functional enzyme activity to prevent the full expression of the disorder.1

This deficiency leads to an increased susceptibility to hemolysis—the premature destruction of red blood cells—particularly when the individual is exposed to certain drugs or oxidative stressors that the body cannot properly neutralize due to the lack of the enzyme.1