GSTM1 and thalassemia: These abnormal globin genes in different combinations lead to more than 60 thalassemia syndromes including three severe thalassemic diseases found in Thailand such as Hb Bart's hydrops fetalis (homozygous α-thalassemia 1, –/–), homozygous β-thalassemia (β+/β+, β+/β0, or β0/β0), and β-thalassemia/Hb E (β+/βE or β0/βE).