Sickle cell disease (SCD) is a common name for several inherited disorders that affect red blood cells. SCD affects about 80,000 people in the United States, making it the most common blood disorder in the country. SCD occurs more frequently in certain populations, such as African Americans. In this population, about one out of every 400 people has the disorder.
SCD occurs in individuals who have defective forms of hemoglobin, the protein in red blood cells that carries oxygen. The defective hemoglobin causes red blood cells to assume an abnormal sickle (or C-like) shape. These irregular-shaped blood cells die early, causing a shortage of red blood cells.
Because anemia causes decreased oxygen in the blood, symptoms may include shortness of breath and fatigue. Anemia may also increase the risk of infections and may delay growth in children.
Sickle cell anemia (SCA), or SS disease, is the most common form of SCD. The terms "sickle cell anemia" and "sickle cell disease" are often used interchangeably.
The defective hemoglobin in SCA is caused by a mutation in a gene that contains the instructions for making hemoglobin. Individuals who inherit two copies of this mutation (one from each parent) will develop SCD. Individuals who inherit only one copy of the mutation may not have symptoms of SCD, but are known as "carriers" because they can pass on the mutation when they have children.
People with SCD are less likely to become infected with malaria, a common infectious disease caused by parasites of the genus Plasmodium (P. falciparum, P. vivax, P. ovale, and P. malariae). This is because the "sickled" red blood cells are somewhat resistant to infection by the malaria parasite. SCD carriers retain some of this resistance to malaria because some of their red blood cells are abnormal. Therefore, SCD occurs more frequently in areas where malaria is also common, including sub-Saharan Africa and other tropical or sub-tropical regions.
Because SCD may decrease oxygen levels in the blood, organs and tissues may be deprived of oxygen and serious damage may result.
Although SCD is a serious condition and generally considered to be incurable, a variety of treatments are available. With proper care, individuals with SCD can maintain relatively healthy lives. Many SCD patients may have normal or near-normal life expectancies.
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types of the disease
General: Sickle cell disease (SCD) is a common name for several inherited disorders that affect red blood cells. These disorders are caused by mutations in the HBB gene, which affect the beta-globin component of hemoglobin. Other mutations can lead to variants of hemoglobin such as hemoglobin C (HbC) and hemoglobin E (HbE). In SCD, at least one beta-globin subunit is replaced with HbS. The remaining beta-globin subunits may have mutations that result in other forms of SCD, such as beta thalassemia.
Sickle cell anemia (SCA): Sickle cell anemia (SCA), or SS disease, is the most common form of SCD. In SCA, the defective form of hemoglobin is called hemoglobin S (HbS). Both beta-globin subunits must have the same mutation to form HbS. The terms "sickle cell anemia" and "sickle cell disease" are often used interchangeably.
Sickle-hemoglobin C (HbSC): If one HbS subunit is combined with one HbC subunit, the resulting disorder is called sickle-hemoglobin C (HbSC) disease.
Sickle-hemoglobin E (HbSE): If one HbS subunit is combined with one HbE subunit, the resulting disorder is called sickle-hemoglobin E (HbSE) disease.
Beta thalassemia: Mutations that result in abnormally low levels of hemoglobin cause a condition known as beta thalassemia. Mild forms of thalassemia are commonly called beta-plus thalassemia, while severe forms are often referred to as beta-zero-thalassemia.
If one HbS subunit is combined with one beta-globin subunit that contains a mutation that causes beta thalassemia, the resulting disorder is called hemoglobin S-beta thalassemia (HbSBetaThal) disease.