HBB and Schnyder corneal dystrophy: SCD results from a single nucleotide substitution (SNS rs334) in the beta globin gene (HBB) that causes the formation of haemoglobin (i.e., HbS), which confers the characteristic sickle shape in erythrocytes, whereas beta-thalassemias can be caused by several mutations (single nucleotide substitution, deletions, insertions, etc.)in the HBB gene [4].