GSTM1 and sickle cell disease: Examples of haemoglobin genotypes considered as sickle cell disorders are sickle cell anaemia/disease (SCA/SCD) (HbSS), sickle cell trait (HbAS), HbSC disease, sickle β-thalassemia disease (S/β thal), HbS with other Hb variants (like D, O-Arab etc.)and HbS/Hereditary persistence of fetal haemoglobin HbS/HPFH (HbSF) [1, 3].