In addition, each globin gene causative mutation is assigned to a single haemoglobinopathy group: (i) Thalassaemia, (ii) Structural Hb (including disease-causing variants, such as HbS and HbE) (iii) Thalassaemia and Structural Hb or (iv) HPFH and, subsequently, it is assigned to one or more haemoglobinopathy subgroups. This evidence concerns the gene GSTM1 and hemoglobinopathy.