GSTM1 and Schnyder corneal dystrophy: Hydroxycarbamide is the gold standard treatment for prevention of painful crises in SCD and has been proven to reduce hospital admissions in patients with SCD.24 Hydroxycarbamide induces fetal haemoglobin (HbF) production, thereby decreasing sickle haemoglobin (Hb) erythrocyte polymers, haemolysis and painful vaso-occlusive crisis.