Thalassemia is an inherited disorder of the blood which has abnormal genes for hemoglobin (Hb) formation. It is one of the less common causes of anemia, the common ones being iron, folic acid, and Vitamin B12 deficiency. However, it is extremely important to be aware of this disorder because children born with major thalassemia have lifelong problems requiring repeated blood transfusions and a shortened lifespan. Therefore, it is necessary to know the risks of thalassemia in pregnancy.
Knowing the right cause of anemia can help a person avoid unnecessary medicines, including excess iron supplementation. The affected persons with minor thalassemia can also keep their Hb at optimum levels by taking the right diet and folic acid supplements if they are aware of its presence.
The exact prevalence of thalassemia in India is not known. It varies with geographic locations and ancestry of the population. The prevalence rate of beta thalassemia mutations in India is as high as 17 percent in some populations. It has been estimated that 0.37 per 1,000 foetus have hemoglobinopathies, which are disorders of haemoglobin formation. This translates to 35-45 million carriers of beta thalassemia minor in our country which is the commonest type of hemoglobinopathy prevalent.
Haemoglobin is an important protein of the body present in blood, which is responsible for transporting oxygen to the tissues. It is formed of heme and 4 peptide chains. The common type of adult Haemoglobin, HbA has 2 alpha and 2 beta chains.
When there is a genetic defect in the production of alpha chain, the resultant thalassemia is called alpha thalassemia and when the defect is in beta chain, the resulting thalassemia is called beta thalassemia. The amount of defects varies. In Beta thalassemia, if both the copies of chromosomes 11 have a defective Beta globin gene, one gets beta thalassemia major.
If the genetic mutation is carried by only one chromosome, it results in beta thalassemia minor. Similarly, depending on the number of alleles (Alpha globin gene) affected in alpha thalassemia, one may be either a silent carrier, trait, HbH disease or alpha thalassemia major.
The minor forms of thalassemia are usually asymptomatic or have mild symptoms of anaemia including pale skin, fatigability etc. These usually lead normal lives and are detected only after specifically testing for hemoglobinopathies. On the other hand, those affected by Thalassemia major are usually diagnosed before 2 years of age. Children suffering from major thalassemia have very low haemoglobin levels, poor growth, decreased appetite, bone deformities, enlarged spleen and liver etc.
As the bone marrow of a thalassemia major individual produces very less haemoglobin, they require blood transfusions every week throughout their life. Apart from the physical and mental pain of getting regular blood transfusions, there are long term problems associated with transfusions which include iron overload, HIV transmission, CMV disease etc. The life spans of these children are usually limited, with many surviving only up to 12- 18 years of age.
Newer treatments in the form of bone marrow transplant and gene therapies are now available, however these are very costly and unavailable at most places. The feasible option therefore today is to prevent the birth of a thalassemia major child.
When only one of the parents, either mother or father, carries an abnormal gene or is beta thalassemia minor, the child can either be normal or have thalassemia minor disorder. But, if both the parents are beta thalassemia minor, there is a 25 percent chance that their child can develop thalassemia major, 50% have thalassemia minor and rest are normal.
Testing both the partners for hemoglobinopathies in the antenatal period or even in the pre-marital stage can thus help in assessing the risk of birth of a thalassemia major child. If only one of the partners is thalassemia minor, there is absolutely no risk of the child getting thalassemia major. However, if both the partners are carriers of thalassemia minor or trait, there will be a 25 percent chance that the unborn child may get thalassemia major.
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Pre-marital counselling and testing of both the parties thus becomes essential. If both the partners are found to carry thalassemia traits, then genetic testing of the unborn fetus at 10-12 weeks of pregnancy by Chorionic Villus Sampling is done to detect if it is a major. The option of continuing the pregnancy or not doing so, is then discussed with the couple.
In certain situations, Preimplantation Genetic Diagnostic Diagnosis (PGD) can also be done to detect whether the embryo carries genes of thalassemia or not. Those embryos who are normal or have minor variants can then be implanted in the womb.
Awareness about this problem can thus help prevent the birth of a thalassemia major child and lifelong problems for the whole family.