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Thalassemia
Thalassemia is a genetic blood disorder. People with thalassemia have too few red blood cells and lower-than-normal hemoglobin.
What Is Thalassemia?
Thalassemia is a blood disorder that runs in families. People who have thalassemia have too few red blood cells and lower hemoglobin than normal.
What Causes Thalassemia?
The type of thalassemia that individuals develop depends on which chain of the hemoglobin is affected. If the alpha chain is defective, alpha-thalassemia results; if the beta chain is defective, beta-thalassemia results. The severity and specifics of the disease also depend on how many defective genes individuals have.
In the case of alpha-thalassemia, one defective gene does not cause individuals to develop any of the symptoms of thalassemia, although they can go on to pass that same defective gene on to offspring. Inheriting two defective genes results in a condition called alpha-thalassemia minor, with only very mild symptoms. Three defective genes results in a condition called hemoglobin H disease, which causes moderately severe symptoms. Four defective genes is termed alpha-thalassemia major or hydrops fetalis, which is fatal to offspring in utero or within a short time after birth.
In the case of beta-thalassemia, one defective gene results in beta-thalassemia minor, which causes mild symptoms; two defective genes results in beta-thalassemia major (also known as Cooley's anemia), which causes moderately severe symptoms. Babies with this condition are usually asymptomatic at birth but develop symptoms of the disease during their first year.
Who Gets Thalassemia?
Thalassemia is one of the most common genetic conditions. It occurs worldwide, but most commonly affects people of Greek, Italian, Middle Eastern, Asian, and African descent. Alpha-thalassemia is particularly common among descendents of people who come from Southeast Asia, China, and the Philippines. People who already know that family members have the disease are obviously at very high risk of having the condition themselves or of passing it on to their offspring.
Some experts believe that the genetic defects of thalassemia have persisted because the abnormal red blood cell configurations actually provide some protection against malaria, because the shape of the thalassemic red blood cells inhibits the entry of the malarial parasite into the cells. Malaria is a serious problem in all the geographic areas where thalassemia has the highest frequency.