Pathophysiology

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Sickle Cell Anemia

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Sickle Cell Anemia is an inherited disease characterized by periods of relative health alternating with episodes of severe illness caused when sickle shaped [pic]red blood cells block small blood vessels. According to the encyclopedia here’s the pathophysiology of the disease; Sickle cell anemia is caused by a mutation in the B globin chain of hemoglobin, causing the amino acid glutamic acid to be replaced with the hydrophobic amino acid valine at the sixth position. The B globin gene is found on the short arm of chromosome 11. The association of two wild type A globin subunits with two mutant B globin subunits forms hemoglobin S. Under low oxygen conditions, the absence of a polar amino acid at position six of the b globin chain promotes the non covalent polymerization (aggregation) of hemoglobin, which distorts red blood cells into a sickle shape and decreases their elasticity. The loss of red blood cell elasticity is central to the pathophysiology of sickle cell disease. Normal red blood cells are quite elastic, which allows the cells to deform to pass through capillaries. In sickle cell disease, low oxygen tension promotes red blood cell sickling and repeated episodes of sickling damage the cell membrane and decreases the cell's elasticity. These cells fail to return to normal shape when normal oxygen tension is restored. These rigid blood cells are unable to deform as they pass through narrow capillaries, leading to vessel occlusion and ischemia (a restriction in blood supply). Sickle cell anemia is a genetic disorder that causes the victim's red blood cells to become stiff and sickle shaped. The disease causes a variety of symptoms, the most prominent of which are crises, caused when the deformed cells block small capillaries, preventing the flow of oxygen to limbs and organs. This blockage is called sludging. The crises range from mild bone aches to devastating body pain and can last up to a week. In the most...
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