HU has multiple benefits in SCD including increases in absolute haemoglobin (Hb), mean corpuscular volume (MCV) and foetal haemoglobin (HbF) levels, reductions in white blood cell (WBC), neutrophil, platelet, and reticulocyte counts, and increased nitric oxide availability. The gene discussed is GSTM1; the disease is Schnyder corneal dystrophy.