Sickle-
cell disease, also called
Sickle-cell anemia, is a group of genetic disorders characterized by an abnormal form of hemoglobin, the oxygen-carrying protein of red blood cells. Offspring of parents who both carry the gene-controlling formation of this sickle-cell hemoglobin (HbS) may inherit SS, the most
common type of disease. When HbS unloads oxygen, it forms a gel of polymers that causes the red blood cells to become stiff and distorted into sicklelike shapes. These cells break up easily,
leading to anemia. They also
damage and clog up blood vessels and impede blood flow, leading to tissue damage and dysfunction of internal organs.
Pain attacks are the most common symptom. Infections and lung damage are the leading cause of death.
In the United States, sickle-cell disease primarily affects African Americans, but it also occurs in some individuals of Mediterranean, Middle Eastern, and Asian Indian descent. An estimated 60,000 Americans suffer from the disease, and about 2.5 million have the sickle-cell trait (AS) and are healthy carriers of the HbS gene. People with sickle-cell trait do not have the common symptoms of the disease but rarely may have bleeding from the kidney. Prospective parents can be tested to determine if they carry the sickle-cell gene or other related abnormal genes that can lead to SS or other types of sickle-cell disease in offspring.
Treatment is largely symptomatic and includes pain relievers, antibiotics, and blood transfusions. Hydroxyurea has been shown to decrease the frequency of pain attacks and need for blood transfusion in adult patients. It is being used with success. New drugs are being tested that interfere with the structure of HbS, preventing it from forming polymers. A 1996 study showed that a bone marrow transplant cured the disease in a significant number of children. However, there are risks associated with bone marrow transplant, including graft-versus-host disease; and in adults, sterility and cancer in later years.
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