Sickle-cell disease

Sickle-cell disease is a genetic disorder in which red blood cells may change shape under certain circumstances. This causes the cells to become stuck in capillaries which deprives the downstream tissues of oxygen and causes ischemia and infarction. The disease usually occurs in periodic painful attacks, eventually leading to damage of internal organs, stroke, or anemia, and usually resulting in decreased lifespan. It is common in people from countries with a high incidence of malaria, and especially in West Africa, or in descendents from those people.

Pathophysiology

Sickle cell anemia is caused by a mutation in the β-globin chain of hemoglobin, replacing glutamic acid with less polar valine at the sixth position of the β chain . The association of two wild type α-globin subunits with two mutant β-globin subunits forms hemoglobin S, which polymerises under low oxygen conditions causing distortion of red blood cells and a tendency for them to lose their elasticity.

Related Topics:
Mutation - Hemoglobin - Glutamic acid - Valine - Wild type - Hemoglobin S - Oxygen

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New erythrocytes are quite elastic, which allows the cells to deform to pass through capillaries. Often a cycle occurs because as the cells sickle, they cause a region of low oxygen concentration which causes more red blood cells to sickle. Repeated episodes of sickling causes loss of this elasticity and the cells fail to return to normal shape when oxygen concentration increases. These rigid red blood cells are unable to flow through narrow capillaries, causing vessel occlusion and ischemia.

Related Topics:
Erythrocytes - Ischemia

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