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Thalassemia is an inherited disorder that affects the production of normal hemoglobin (a type of protein in red blood cells that carries oxygen to the tissues of the body). Thalassemia includes a number of different forms of anemia. The severity and type of anemia depends upon the number of genes that are affected.
Alpha thalassemia is caused by mutations in the alpha chain of the hemoglobin molecule. Normally, there are two alpha chain genes located on each #16 chromosome, for a total of 4. The alpha chain is an important component of fetal hemoglobin (which is usually made before birth) and hemoglobin A and hemoglobin A2 (which are present after birth). How these genes are altered determines the specific type of alpha thalassemia in a child:
When parents are carriers of the cis deletion, there is a one in four, or 25 percent, chance with each pregnancy, to have a baby with alpha thal major. Carriers of the cis deletion versus the trans deletion can be distinguished by DNA analysis only. DNA testing is usually done from a blood sample, to look at the alpha chain genes on each #16 chromosome, to determine which are deleted.
Alpha thalassemia is most commonly found in Africa, the Middle East, India, Southeast Asia, southern China, and the Mediterranean region. Carrier status can be determined by the following:
All of these studies can be performed from a single blood sample. Prenatal diagnosis is determined from CVS (chorionic villus sampling) or amniocentesis.
Specific treatment for alpha thalassemia will be determined by your child's physician based on:
Treatment for alpha thalassemia may include:
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