Thalassaemia

Thalassaemia is the name given to a group of inherited blood disorders that affect the body's ability to create red blood cells.

Red blood cells

Red blood cells are very important because they carry a protein called haemoglobin around the body. Haemoglobin takes oxygen from our lungs to the rest of the body.

Haemoglobin is produced in our bone marrow (a red spongy material found inside the larger bones) using the iron that our body takes from our food.

If your body does not receive enough oxygen, you will feel tired, breathless, lethargic and faint. This condition is known as anaemia. The most serious types of thalassaemia can cause other complications including organ damage, restricted growth, liver disease, heart failure and death.

Types of thalassaemia

Thalassaemia is caused by alterations (mutations) in the genes that make haemoglobin.

Haemoglobin is made up of matching chains of proteins (named after Greek letters of the alphabet). To work properly, haemoglobin needs both an alpha chain and a beta chain.

A mutation that affects the alpha chain causes alpha thalassaemia, and a mutation that affects the beta chain causes beta thalassaemia.

Alpha thalassaemia
The alpha chain is produced by four genes. The severity of the condition depends on how many of those genes have mutated.

• If one gene is mutated there is little or no effect.
• If two genes are mutated there may be symptoms of mild anaemia. This condition is known as the alpha thalassaemia trait. If two people with the alpha thalassaemia trait have a child, there is a 25% chance that their child will inherit the most severe form of alpha thalassaemia (see below).
• If three genes are mutated the result will be a condition called Haemoglobin H disease. People with Haemoglobin H disease will have life-long (chronic) anaemia, and may require regular blood transfusions.
• If all four genes are mutated the result will be the most severe form of alpha thalassaemia, known as alpha thalassaemia major. Infants with this condition are unable to produce normal haemoglobin and are unlikely to survive pregnancy. There have been some cases of unborn babies being treated with blood transfusions while they are still in the womb, but the success rate of this type of treatment is not high.

Beta thalassaemia
Beta thalassaemia can range from moderate to severe. The most severe form of the condition is known as beta thalassaemia major (BTM). People with BTM will require blood transfusions for the rest of their lives.

The more moderate form of the condition is known as beta thalassaemia intermediate (BTI). The symptoms of BTI will vary from person to person. Some will experience only symptoms of mild anaemia while others will require blood transfusions.

The only known cures for thalassaemia are bone-marrow transplant and cord blood transplantations (using blood cells taken from a foetus carried by a mother who also has an older affected child). These procedures can cause other complications and are not suitable for everyone.

This article will focus mainly on beta thalassaemia because it is the most common and severe form of the condition in the UK. While alpha thalassaemia can be found in the UK, particularly among people of South Asian and South-East Asian descent, it is typically the mildest form of the condition.

Thalassaemia is more common in people who originate from the Mediterranean basin, the Middle East, South Asia and East Asia. In the UK the condition occurs most often among people of Cypriot, Italian, Greek, Indian, Pakistani, Bangladeshi and Chinese descent. This is because the mutations that cause thalassaemia originally occurred in countries in which malaria was common.