Sales and colleagues utilized a systematic review and found 50 different SNPs of 17 genes to be associated with HbF changes in patients with SCD treated with hydroxyurea that are VEGF ligand–receptor interactions (R-HSA-194313; R-HSA195399) and the urea cycle(R-HSA-70635) [166]. This evidence concerns the gene ALB and Schnyder corneal dystrophy.