GSTM1 and Schnyder corneal dystrophy: Sickle cell disease (SCD) is an inherited autosomal recessive genetic disease of haemoglobin (Hb) caused by a mutation of the β-globin gene of haemoglobin, which leads to the substitution of a single nucleotide from thymine to adenine in haemoglobin, resulting in the amino acid valine instead of glutamic acid [3].