Do you recommend hydroxyurea in patients with sickle cell disease with hereditary persistence of fetal hemoglobin who have recurrent vaso-occlusive crises requiring hospital admission?  

If hydroxyurea modifies the course of sickle cell disease by increasing fetal hemoglobin, is there any benefit to using it in patients with fetal hemoglobin over 20% if they continue to have several pain crises? Are there other mechanisms that contribute to disease modification? Would you consider voxelotor in these situations?