Effect of Hydroxyurea on the Frequency of Painful Crises in Sickle Cell Anemia

Sickling of red cells in patients with sickle cell anemia is caused by the polymerization of molecules of deoxygenated hemoglobin S (α 2 β 2 s) into rigid, rod-like polymers. Fetal hemoglobin (α 2 γ 2 ), which lacks β-globin chains, inhibits sickling in vitro by interfering with the polymerization of hemoglobin S. Clinical observations have suggested that increased fetal hemoglobin concentrations may have beneficial effects in sickle cell anemia. 1 Considerable interest was aroused by the discovery that the administration of 5-azacytidine to adult baboons stimulated the production of fetal hemoglobin. 2 Other cytotoxic agents had a similar effect, 3 – 5 but . . .