These malaria relapses arise from dormant liver stages (hypnozoites) that are refractory to most antimalarial drugs.4, 5, 6 Relapse is the main cause of vivax illness in endemic areas.6, 7 Primaquine, an 8-aminoquinoline, is the only widely available drug that kills hypnozoites and prevents relapses,8 but its use is limited by the risk of acute haemolysis in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. The gene discussed is G6PD; the disease is malaria.