Sickle cell disease is a molecular disease of Haemoglobin (Higgins, Eddington, Bhatia, & Mahadevan, 2007). The disorders of hemoglobin (haemoglobinopathies), can be divided into two main groups: the structural variants - HbS, HbC and HbE (Alanazi et al., 2011) and disorders of production of the globin chains which leads to thalassemia. The mutant haemoglobin HbS, HbC and HbE are associated with the sickling disorder. The abnormal hemoglobin is less soluble than normal haemoglobin A and, therefore, tends to crystallize out resulting in deformation of the cells which instead of being disc-shaped become sickle-shaped. Sickle cell disease is inherited as an autosomal recessive characteristic. The disease manifested in persons who are homozygous for the gene. If the mutant haemoglobin is inherited from both parents, the genotype of such offspring will be HbSS, HbCC or HbEE. But if from only one parent, the genotype would be heterozygous HbAS, HbAC or HbAE. Also, an offspring can be compound heterozygote e.g. SC and SE among others (Weatherall, Akinyanju, Fucharoen, Olivieri, & Musgrove, 2006)
The molecular basis for erythrocyte sickling is a single nucleotide substitution in codon 6 of the β-globin gene leads to an amino acid substitution (Glu→Val) that is responsible for the sickle mutation in beta-globin (β S), which forms the abnormal HbS tetramer (Kazazian et al., 1992). Upon deoxygenation, HbS undergoes rapid intracellular polymerization with subsequent cellular dehydration, becoming sickled, and adversely affecting the usual physiologic deformability of erythrocytes that allows them to traverse the circulation freely. These rigid and deformed sickle erythrocytes have a shortened lifespan and undergo both intravascular and extravascular hemolysis. Clinical manifestations of sickle cell anemia include acute vaso-occlusive events, chronic hemolytic anemia, and organ