sickle cell anemia
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sickle cell anemia
A chronic, severe, and sometimes fatal anemia marked by crescent-shaped red blood cells and characterized by fever, leg ulcers, jaundice, and episodic pain in the joints. The disease occurs in people who are homozygous for a gene that produces an abnormal form of hemoglobin, and it is found chiefly in people of African descent and in some Mediterranean, Middle Eastern, Central and South American, and South Asian populations. Also called sickle cell disease.
sick′le cell` ane′mia
a chronic hereditary blood disease, primarily affecting indigenous Africans and their descendants, in which an accumulation of oxygen-deficient sickle cells results in anemia, blood clotting, and joint pain.Also called sicklemia.
sick·le cell anemia(sĭk′əl)
A hereditary disease characterized by red blood cells that are sickle-shaped instead of round because of an abnormality in the hemoglobin, the protein that carries oxygen in the blood. Because of their shape, the cells can cause blockage of small blood vessels in the organs and bones, reducing the amount of oxygen available to those tissues.
Did You Know? Genetic mutations can be good or bad, and sometimes they can even be both. The mutation that causes sickle cell anemia is one example. It is harmful if a person inherits two copies of the mutated gene (one from each parent), but there is actually some benefit if only one copy of the gene is inherited. The defective gene causes red blood cells to be distorted into a sickle shape, which makes it hard for them to pass through the tiny blood vessels where they give oxygen to body tissues. If a person's chromosomes have two copies of the mutated gene, serious sickle cell anemia results, causing illness. With just one copy of the gene, though, only some mild sickling of the cells occurs. It so happens that this mild sickling is harmful to the parasite that causes malaria, and can protect a person from that disease. In a region like tropical Africa where malaria is common, people who have the mutation in one gene are more likely to ward off a malarial infection and to live long enough to have children, who then inherit the gene in turn. And because inheriting two copies of the gene is much less likely than inheriting just one, the benefits of the gene outweigh its risks for most people in these regions.