What is Sickle Cell Anemia?

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Sickle cell anemia is an inherited blood disorder, characterized primarily by chronic anemia and periodic episodes of pain.

The underlying problem involves hemoglobin, a component of the red cells in the blood. The hemoglobin molecules in each red blood cell carry oxygen from the lungs to the body organs and tissues and bring back carbon dioxide to the lungs.

In sickle cell anemia, the hemoglobin is defective. After the hemoglobin molecules give up their oxygen, some of them may cluster together and form long, rod-like structures. These structures cause the red blood cells to become stiff and to assume a sickle shape. Unlike normal red cells, which are usually smooth and donut-shaped, the sickled red cells cannot squeeze through small. blood vessels. Instead, they stack up and cause blockages that deprive the organs and tissue of oxygen-carrying blood. This process produces the periodic episodes of pain and ultimately can damage the tissues and vital organs and lead to other serious medical problems.

Unlike normal red blood cells, which last about 120 days in the bloodstream, sickled red cells die after only about 10 to 20 days. Because they cannot be replaced fast enough, the blood is chronically short of red blood cells, a condition called anemia.

The abnormal hemoglobin molecules tend to cluster together and from long, rod like structures. These structures cause some of the red blood cells to become stiff and to assume a sickle shape.

What causes Sickle Cell Anemia

Sickle cell anemia is caused by an error in the gene that tells the body how to make hemoglobin. The defective gene tells the body to make the abnormal hemoglobin that results in deformed red blood cells. Children who inherit copies of the defective gene from both parents will have sickle cell anemia. Children who inherit the defective sickle hemoglobin gene from only one parent will not have the disease, but will carry the sickle cell trait. Individuals with sickle cell trait generally have no symptoms, but they can pass the sickle hemoglobin gene on to their children.  Click here for illustrations...

The error in the hemoglobin gene results from a genetic mutation that occurred many thousands of years ago in people in parts of Africa, the Mediterranean basin, the Middle East, and India. A deadly form of malaria was very common at that time, and malaria epidemics caused the death of great numbers of people.

Studies show that in areas where malaria was a problem, children who inherited one sickle hemoglobin gene and who, therefore, carried the sickle cell trait - had a survival advantage. Unlike the children who had normal hemoglobin genes, they survived the malaria epidemics they grew up, had their own children, and passed on the gene- for sickle hemoglobin.

As populations migrated, the sickle cell-mutation spread to other Mediterranean areas, further into the Middle East and eventually into the Western Hemisphere. In the United States and other countries where malaria is not a problem, the sickle hemoglobin gene no longer provides a survival advantage. Instead, it may be a serious threat to the carrier's children, who may inherit two abnormal sickle hemoglobin genes and have sickle cell anemia.