Thalassemia

What is Thalassemia?

Thalassemia is a hereditary disease affecting the production of haemoglobin in the red blood cells, resulting in chronic haemolytic anaemia. The disease is common in the Mediterranean, Middle East and Southeast Asian regions.

Types of Thalassemia

There are several types of thalassemia. Depending on the clinical severity of the disease, it can be classified into thalassemia major, thalassemia intermedia and thalassemia minor etc. Thalassemia minor is common in Hong Kong, estimated to affect about 8.5% of the population.

Symptoms of Thalassemia

Most cases of alpha thalassemia major develop symptoms in the fetal or infant stage and die. Babies with beta thalassemia major require life long blood transfusions.

Patients with thalassemia minor do not have obvious symptoms and can lead a normal life. Some women may become anaemic during pregnancy. The point of greatest concern, however, is that the thalassemia gene can be transmitted to the next generation.

How would Thalassemia affect your offsprings?

Generally speaking, a couple with the same type of thalassemia minor have a chance of giving birth to a baby with thalassemia major:

In other words, when both parents are carriers, the child has a one-in-four chance of having thalassemia major; a two-in-four chance of having thalassemia minor; and a one-in-four chance of being normal.

Therefore, thalassemia should not be overlooked because it can seriously affect the next generation.

Blood Test

Although thalassemia minor does not present with noticeable symptoms, it can be detected through blood tests.

Couples planning to have children should undergo pre-pregnancy blood tests and physical check-up. Preliminary screening test showed low red blood cell size, they should consult their doctor to determine their type of thalassemia and their chance of having a baby with severe thalassemia.

If a pregnant woman is suspected to be carrying an affected baby, what can be done?

A woman should undergo prenatal diagnosis as early as possible during pregnancy if the fetus is suspected to have thalassemia major. Prenatal diagnosis by chorionic villus sampling (CVS) or amniocentesis can detect the thalassemia gene in the fetus, and fetal blood sampling can be performed to study the globin chain synthesis. If the fetus is diagnosed as thalassemia major, the couples can decide whether or not to continue the pregnancy.

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