GSTM1 and thalassemia: β-thalassemia results from mutations in the HBB gene affecting β-globin, while α-thalassemia is caused by deletions or mutations in the HBA1 and HBA2 genes affecting α-globin, resulting in diminished or absent synthesis of the α-globin chain of hemoglobin (Hb) (Chen et al.,2002; Muncie and Campbell, 2009).