Thalassaemia – A brief introduction
Mrs. Chan was told by her doctor that she has beta thalassaemia minor after her recent antenatal blood check and was told to bring her husband to have a blood test for thalassaemia screening. Fortunately her husband was found to be negative for thalassaemia and so there is no chance that their children will suffer from the severe form of thalassaemia (thalassaemia major). The doctor told them that even if their child inherits the thalassaemia gene from her, there would be no clinical consequence and can still lead an active normal life. Her doctor even told her that former professional tennis player Pete Sampras and former professional football player Zinedine Zidane are known to have thalassemia minor!
What is thalassaemia?
To understand thalassaemia, one should have some basic understanding of blood cells and haemoglobin. Blood appears red in colour because of the haemoglobin in red cells, which functions to carry oxygen from the lung to all body tissues. Anaemia results when the concentration of red cells or haemoglobin in blood falls to below the normal lower limit. In normal adults, over 95% of haemoglobin are composed of haemoglobin A, with the globin part composed of 4 globin chains (α2β2), with 1 α and 1 β chain being contributed by each parent. As a result, there are two main types of thalassaemia due to defect of the α globin gene (alpha thalassaemia) or β globin gene (beta thalassaemia).
Thalassaemia got its name as it is derived from the Greek word “thalassa” meaning the sea because the condition was first described in patients living near the Mediterranean Sea. This condition is also prevalent in Asia, Middle East, Caribbean regions and Africa. In Hong Kong about 5% of people has alpha thalassaemia and about 3% has beta thalassaemia with the great majority of them being thalassaemia minor. Thalassaemia minor is due to defect in 1 alpha or beta globin gene and such patients usually has normal or mildly decreased haemoglobin level with no clinical symptoms. Thalassaemia major is a severe disease due to both alpha or beta genes being defective resulting in severe degree of anaemia. Beta thalassaemia major patients require life-long blood transfusion and drugs for removal of the excess iron accumulated in the body due to the blood transfusion given.
One well known artist in Hong Kong, Mr. Stephen Cheng Sze Kwan, has beta thalassaemia major and is leading a relatively normal life despite this medical condition and its treatment. However, alpha thalassaemia major, with all alpha genes being deleted or defective, is incompatible with life and the affected baby usually die at the later stage of pregnancy or soon after birth.
How to prevent thalassaemia major?
As thalassaemia is an inherited disease and so the prevention of thalassaemia major lies mainly on minimizing the risk of giving birth to babies with such condition. A simple blood test could usually tell if a person is carrying the alpha or beta thalassaemia gene. If two alpha thalassaemia minor or beta thalassaemia minor persons get married, their children have 25% chance of having thalassaemia major, 50% chance of having thalassaemia minor, and 25% chance of being completely.It is highly recommended that genetic testing and counseling be provided to such couples with high risk of giving risk to thalassaemia major babies, which would dramatically decrease the chance of giving birth to a baby with thalassaemia major.
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