Sickle cell disease is due to homozygous inheritance of the hemoglobin S mutation (Hb SS) or compound heterozygous inheritance of the Hb S mutation with another β-globin chain abnormality, such as Hb C (Hb SC) or β-thalassemia (Hb Sβ+-thalassemia, Hb Sβ0-thalassemia). This evidence concerns the gene GSTM1 and thalassemia.