G6PD and hyperinsulinemic hypoglycemia, familial, 4: Counterbalancing these deleterious effects is evidence that suggests G6PD deficiency confers partial protection against malaria, and that such protection has conferred a selective advantage to G6PD-deficient individuals in malaria-endemic regions, as reflected in the close geographical correlation between the global distribution of G6PD deficiency and that of historical malaria endemicity.