GSTM1 and Schnyder corneal dystrophy: SCD is an inherited blood disorder caused by a pathogenic substitution mutation in the β-globin gene that replaces the hydrophilic amino acid glutamine with the hydrophobic valine at the sixth position of the β-globin chain, resulting in the formation of a poorly soluble form of hemoglobin (Hb), Hb S. In a low oxygen state, Hb S polymerizes and becomes distorted and rigid, causing the red cells to change their morphology and show the characteristic of a sickle cell form [2,3].