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G6PD deficiency

Thursday 2 March 2006

Transmitted on the X chromosome, G6PD deficiency, which predisposes to red cell hemolysis in patients receiving certain types of drugs, is expressed principally in males.

In the female, a proportion of the red cells may be derived from marrow cells with inactivation of the normal allele. Such red cells are at the same risk for undergoing hemolysis as are the red cells in the hemizygous male.

Thus, the female is not only a carrier of this trait, but also is susceptible to drug-induced hemolytic reactions.

Because the proportion of defective red cells in heterozygous females depends on the random inactivation of one of the X chromosomes, however, the severity of the hemolytic reaction is almost always less in heterozygous women than in hemizygous men.