GSTM1 and Schnyder corneal dystrophy: Sickle cell disease (SCD) is an inherited disorder characterized by the presence of hemoglobin (Hb) S. It manifests as a homozygous state (HbS/S) or double heterozygous state, when HbS is co-inherited with other Hb variants such as β-thalassemia, Hemoglobin C (HbC), Hemoglobin D-Punjab (HbD Punjab), Hemoglobin E (HbE), and others (1).