Improvement in hemoglobin and reduction in painful episodes was observed with hydroxyurea treatment [9]. Similar observations were made in another study comparing the phenotypic expression of HbSS and HbSD which stated that fetal Hb and alpha thalassemia modulate the phenotypic expression of HbSD-Punjab [10]. HbF had a protective effect on the frequency of VOC in HbSD. Here, GSTM1 is linked to Alpha-thalassemia.