GSTM1 and Beta-thalassemia: Nemati et al (2010) have studied the frequency of XmnI polymorphic site in beta-thalassemia major patients from Western Iran and has revealed that the presence of this polymorphic site caused a positive influence on Hb F production and the (G) gamma % which could improve the clinical symptoms of beta-thalassemia patients.14 Similar results are observed in our study.