Genetically, Hb H disease is caused by interaction of α0‐ thalassemia and α+‐thalassemia, which can be divided into a deletional form (deletion of three α‐globin genes) and non‐deletional form (deletion of two α‐globin genes compound a non‐deletional mutation), leaving only one intact α‐globin gene. Here, GSTM1 is linked to thalassemia.