GSTM1 and Schnyder corneal dystrophy: A total of 693 NB (75.4%) were heterozygous for Hb S; in that, 676 Hb FAS (sickle cell trait; 73.6%), and 17 Hb FAS (1.8%) with coinheritance of alpha-thalassemia; nine (0.9%) had SCD (four with SCA – homozygous for Hb S – Hb FS and five were double-heterozygous for Hb S and Hb C – Hb SC).