sickle cell anemia
The definitions used in this glossary of terminology either have been provided by the authors of the articles, or have been extracted wholly or in part, or paraphrased from the following sources: The American Medical Association Encyclopedia of Medicine, Charles B. Clayman, MD, Medical Editor, Random House, New York, 1989; Biotechnology from A to Z, 2d Edition, William Bains, Oxford University Press, New York, New York, 2002; A Dictionary of Genetics, 6th Edition, Robert C. King and William D. Stansfield, Oxford University Press, New York, New York, 2002; Dorland's Illustrated Medical Dictionary, 29th and 30th Editions, W. B. Saunders Company, Philadelphia, 2000, 2003; Genes VII, Benjamin Lewin, Oxford University Press, New York, New York, 2000; The Gale Encyclopedia of Genetic Disorders, Volumes I and II, Stacey L. Blachford, Ed., Thomson Learning, New York, New York, 2002; The Merriam-Webster Dictionary, Merriam-Webster, Inc., Springfield, Massachusetts, 1997; Molecular Biology of the Cell, 3rd Edition, Bruce Alberts, et al., Garland Publishing, 1994; The Random House Dictionary of the English Language, Unabridged Edition, 1966; Webster's Ninth New Collegiate Dictionary, 1991.
DEFINITION:
- sickle cell anemia
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An inherited blood disease that occurs primarily in blacks, and less commonly, in individuals of Mediterranean origin. In sickle cell anemia, the red cells are abnormal, resulting in a chronic, very severe form of anemia (reduced oxygen-carrying capacity of the blood).
The red cells of affected people contain an abnormal type of hemoglobin (oxygen-carrying pigment) called hemoglobin S. In the blood capillaries, where blood is less oxygenated, the deficiency of oxygen causes hemoglobin S to crystallize, distorting the red cells into a sickle shape. This makes the cells fragile; they are easily destroyed, leading to hemolytic anemia. Also, the abnormal cells are unable to pass easily through tiny blood vessels, so they may intermittently block blood flow to various organs, causing sickle cell crises.
Sickle cell anemia occurs in a person who has inherited hemoglobin S from both parents. If hemoglobin S is inherited from one parent, the person has sickle cell trait and is usually free of symptoms. If two such carriers have a child, there is a 1 in 4 chance that the child will have sickle cell anemia, a 2 in 4 chance that the child will have sickle cell trait, and a 1 in 4 chance that the child will have neither.
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