The odds ratio of methemoglobinemia was two times higher in children with hemoglobinopathies (sickle cell anemia or glucose-6-phosphate dehydrogenase deficiency (G6PD)) (aOR 1.97, 95 % CI: 1.17, 3.32), or in severe anemia (aOR 1.99, 95 % CI: 1.51, 2.61). The gene discussed is G6PD; the disease is hemoglobinopathy.