The pathogenesis of secondary congenital erythrocytosis involves defects in the oxygen sensing pathway, with multiple target components, notably hypoxia-induced factors, prolyl hydroxylases, and von Hippel-Lindau proteins or EPO gene defects (methemoglobinemia, bisphosphoglycerate mutase deficiency, alteration in α and β globin genes)2,11. The gene discussed is EPO; the disease is polycythemia.