Unlike the case observed in most normal adult humans where the commonest hemoglobin type (hemoglobin A or Hb A) is a tetramer (which contains 4 subunit proteins- α2β2A that are non-covalently bound together), patients with SCD have an adult hemoglobin type with two mutant β subunits (called βS) called hemoglobin S (or simply, Hb S) [3,4]. This evidence concerns the gene GSTM1 and Schnyder corneal dystrophy.