The phenotype of α-thalassemia is directly related to the number of α-globin genes affected and can be classified into several categories: α+-thalassemia (-α/αα or αTα/αα), α0-thalassemia (--/αα or -α/-α), HbH disease (--/-α or --/αTα), and Hb Bart’s hydrops fetalis syndrome (--/--). This evidence concerns the gene GSTM1 and thalassemia.