Sickle cell anemia is due to:

Sickle cell disease is a hereditary hemoglobinopathy, characterized by the defective haemoglobins. It is caused by a point mutation at the sixth position of the beta globin chain leading to substitution of valine residue for a glutamic acid residue. In homozygous state -100 % chains defective i.e., no HbA In heterozygous state -40 % chains defective i.e., HbA present HbA = α2β2 Hb A2 = α2δ2 HbF = α2γ2 • Most important factor which affects degree of sickling is amount of Hb S and its interaction with other Hb chains Factors favouring polymerization ■ Hypoxia -↑2,3 BPG → ↑ polymerization ■ Acidosis - ↑ acidosis → ↑ polymerization ■ Hb concentration -1 Hb concentration →↑ polymerization ■ Combination with other hemoglobins - already discussed