A group of inherited disorders of the beta-hemoglobin chain is known as sickle cell disease (SCD). Hemoglobin A, A2, and F are the three types of hemoglobin found in normal blood. In sickle cell disease, hemoglobin S has an abnormal beta globin chain that is encoded by a glutamic acid to valine conversion on chromosome 11. (Bunn,2007). This condition is autosomal recessive. A person with sickle cell disease has a particular genotype in which they inherit one copy of the HbS gene and another gene that codes for a beta globin chain that is either qualitatively or quantitatively abnormal. Patients with sickle cell anemia (HbSS) are homozygous for the HbS gene, whereas heterozygous forms can combine HbS with genes coding for other types of abnormal hemoglobin, such as hemoglobin C, an autosomal recessive disorder.

recessive mutation that changes glutamic acid to lysine. Additionally, a person may inherit both HbS and -thalassemia. The -thalassemias are autosomal recessive disorders that cause anemia by reducing or eliminating -globin chains. HbSD, HbSO-Arab, and HbSE are additional genotype pairs (Meremiku, 2008).

Red blood cells with sickle hemoglobin in these disorders polymerize when oxygen tension is low, giving the red blood cells the distinctive sickle shape. Normal red blood cells last in the blood stream for about 120 days, but sickled red blood cells pass away after 10 to 20 days. The blood is chronically deficient in red blood cells due to their inability to be replaced quickly, a condition known as anaemia. Microcirculation-based sickle cell accumulation brought on by thrombophilia, endothelial abnormalities, and inflammation cause ischemia in tissues and end organs far from the blockage (Hayes, 2004).


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