G6PD deficiency is also called Clucose-6-Phosphute Dehydrogenase Deficiency. A severe hemolytic anemia (favism) may be produced by the ingestion of the broad bean Vicia fava. The anemia is due to deficiency of the X-linked enzyme glucose-6-phosphate dehydrogenase in the erythrocytes of susceptible subjects (see Glucose-6-Phosphate Dehydrogenase in Ch. 740). It is of interest that a deficiency of the enzyme is a necessary but not sufficient cause for the anemia that follows ingestion of fava beans. Additional genetic factors, presently poorly identified, are also required if the disease is to be manifest. Severe neonatal jaundice in the Mediterranean basin and Far East may occasionally be associated with glucose-6-phosphate dehydrogenase deficiency.
Persons with glucose-6-phosphate dehydrogenase deficiency are particularly susceptible to hemolytic reactions after administration of the antimalarial drug primaquine and certain other drugs, including aspirin and phenacetin. The mutation in the black population is characterized by a mean enzyme activity of 10 to 20 per cent of normal, and the increased susceptibility to hemolysis is restricted to the older red cells. The risk of hemolysis is significantly less than in the Mediterranean type of glucose-6-phosphate dehydrogenase deficiency in which the residual enzymatic activity is less than 5 per cent of normal and increased susceptibility to hemolysis occurs in young as well as old cells. Interestingly, a severe hemolytic anemia may occur during the course of acute viral hepatitis and infectious mononucleosis in individuals with deficiency of glucose-6-phosphate dehydrogenase.
The trait is present in about 10 per cent of blacks in the United States and may reach as high as 35 per cent in certain African and Mediterranean population tions. The deficiency provides some protection against falciparum malaria and accounts for the persistence of the gene at a very high level in these populations. The relationship of glucose-6-phosphate dehydrogenase deficiency and resistance to falciparum malaria affords one of the better examples of a balanced polymorphism in which a heterozygous advantage can be clearly demonstrated.