It is thought that the series of genetic mutations associated with thalassaemia originally evolved as a defence against malaria. Those with mutated forms of haemoglobin had a higher resistance against malaria.
This is why thalassaemia, and other related genetic blood disorders such as sickle cell anaemia, are more common in parts of the world where malaria was rife, such as:
- countries in the Mediterranean basin such as Greece, Cyprus and Italy
- the Middle East
- Asia
- Africa
How thalassaemia is inherited
Every person receives two sets of genes, one from their father and one from their mother. If a person receives one set of mutated genes, they will have the thalassaemia trait.
If they then have a baby with somebody who also has the thalassaemia trait, there is significant chance that the baby will receive two sets of mutated genes and develop thalassaemia.
The chances of the thalassaemia trait being passed on are outlined below:
- There is a one-in-four chance that the baby will receive a pair of normal haemoglobin genes.
- There is a one-in-two chance that the baby will receive one normal gene and one mutated gene. In this case, they will not have thalassaemia, but they will have the thalassaemia trait.
- There is a one-in-four chance that the baby will receive a pair of mutated genes and will have thalassaemia.
If one parent has the thalassaemia trait and the other parent has normal haemoglobin, their baby will not get thalassaemia. However, there is a one-in-two chance that the baby will receive the thalassaemia trait.
Beta thalassaemia affects the two genes that the body uses to produce the beta chain found in haemoglobin. (Haemoglobin needs both an alpha and beta chain to work properly.)
If only one gene is mutated, the result is the beta thalassaemia trait. This produces either very mild symptoms of anaemia or, more commonly, none at all.
Beta thalassaemia major (BTM) occurs when both genes that produce the beta chain mutate. People with BTM are unable to produce normal haemoglobin and will require regular blood transfusions for the rest of their life.
