The only known therapies effective against latent vivax malaria, 8-aminoquinoline drugs, invariably provoke acute hemolytic anemia in patients deficient in glucose-6-phosphate dehydrogenase (G6PD)—a highly polymorphic inherited disorder affecting an average of 8% of residents of malaria-endemic nations. The gene discussed is G6PD; the disease is Plasmodium vivax malaria.