|AGE Present from birth; age at first appearance of symptoms depends on type||GENDER Not significant factors|
|LIFESTYLE Not significant factors||GENETICS Due to an abnormal gene inherited from one or both parents|
Thalassaemia is an inherited type of anaemia affecting production of haemoglobin, the oxygen-carrying pigment in red blood cells.
In thalassaemia, an inherited genetic defect prevents the normal formation of haemoglobin, the oxygen-carrying pigment inside red blood cells. Red cells containing the defective haemoglobin carry less oxygen than normal and are destroyed prematurely, reducing oxygen transport to the body tissues.
The body tries to compensate by producing additional red blood cells throughout the bone marrow and in the liver and spleen, where blood cells are not normally formed. The marrow expands due to overactivity, which may lead to thickening of the bones of the skull and face. The liver and spleen may become enlarged as they produce and, in the case of the spleen, destroy large numbers of the abnormal red blood cells. Thalassaemia mainly affects people from Mediterranean countries, the Middle East, Southeast Asia, and Africa.
What are the causes of thalassaemia?
A normal haemoglobin molecule contains four protein (globin) chains: two alpha and two beta chains. Different genes are responsible for the production of each type of chain. Thalassaemia is caused by one or more genetic defects and results in a failure to produce sufficient quantities of either the alpha or the beta globin chains.
Thalassaemia due to abnormal beta chains is more common. If a defective gene for beta-thalassaemia is inherited from only one parent, there may be no symptoms. Inheritance of a defective gene from each parent in an autosomal recessive pattern (see Gene disorders) leads to a more severe condition.
There are two copies of the gene responsible for haemoglobin alpha chains. People who have one abnormal gene for alpha-thalassaemia usually have no symptoms, but a fetus with two defective genes will die before birth.
Can it be prevented?
In communities in which thalassaemia is particularly common, genetic testing may be offered to couples planning to have children. If a defective gene is identified, they may want to consider genetic counselling. If a woman or her partner is known to have the disorder, tests can be done to establish whether the fetus has inherited the genetic defect (see Antenatal genetic tests).
What are the symptoms of thalassaemia?
People who have alpha-thalassaemia or mild forms of beta-thalassaemia do not usually have symptoms. However, if the defective gene for beta-thalassaemia is inherited fromboth parents, symptoms of severe anaemia usually appear between 4 and 6 months of age. These symptoms may include:
- Pale skin.
- Shortness of breath on mild exertion.
- Swelling of the abdomen due to an enlarged spleen and liver.
Affected children have slow growth, and sexual development is delayed. The bones of the skull and face may thicken as the bone marrow expands.
What might be done?
If your doctor suspects that you have thalassaemia, he or she may arrange for blood tests to confirm the diagnosis.
If the thalassaemia is mild, you may not require treatment, but you may be advised to take folic acid supplements (see Vitamins) to help to stimulate the production of red blood cells. If the condition is severe, regular blood transfusions may be needed for life. However, frequent blood transfusions can lead to a build-up of iron in the heart, liver, and pancreas, causing progressive damage to these organs. To counteract this build-up, treatment with desferrioxamine (a drug that allows the kidneys to excrete more iron than usual) may be needed. If the spleen is enlarged, it may need to be removed. In severe cases, a stem cell transplant may be considered.
What is the prognosis?
People with mild thalassaemia have a normal life span. Some people who have severe thalassaemia die early in childhood, but life expectancy can be greatly improved with regular transfusions.
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