While mean Hb level among children with SCD was more than 2 g/dL below than that of non-sickle cell children (8.04 g/dL versus 10.19 g/dL), mean Hb level of children with sickle cell trait was close to that of the latter (10.14 g/dL) (Table 2). This evidence concerns the gene GSTM1 and Schnyder corneal dystrophy.