Thalassaemia is a group of inherited blood disorders where the haemoglobin in the blood is abnormal.
The abnormality means that the affected red blood cells are unable to function normally, which leads to anaemia (a red blood cell deficiency).
Red blood cells
Red blood cells are very important because they contain a substance called haemoglobin, which carries oxygen from the lungs to the rest of the body.
Haemoglobin is produced in the bone marrow (a spongy material found inside larger bones) using the iron that the body gets from food.
In thalassaemia, haemoglobin production is abnormal, leading to anaemia and a reduced oxygen-carrying capacity. If your body doesn't receive enough oxygen, you'll feel tired, breathless, drowsy and faint.
If left untreated, 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, which are named after Greek letters of the alphabet. To work properly, haemoglobin needs a pair of alpha chain and a pair of beta chain proteins.
A mutation that affects the alpha chain causes alpha thalassaemia, and a mutation that affects the beta chain causes beta thalassaemia.
The alpha chains are produced by four genes, two on each chromosome 16, inherited as pairs. The severity of the condition will depend on how many of those genes have been altered.
If one gene is mutated, there's little or no effect. If two genes are mutated (one on each chromosome), there may be symptoms of mild anaemia. This condition is known as the alpha thalassaemia trait.
If two people with the alpha thalassaemia zero trait (when two genes on the same chromosome are altered) have a child, there's a one in four chance of the child inheriting the most severe form of alpha thalassaemia.
If three genes are mutated, the result will be a condition called haemoglobin H disease. Someone with this condition will have lifelong (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 still in the womb, but this type of treatment has a low success rate.
Alpha thalassaemia is a blood disorder that occurs worldwide. It's particularly common in Southeast Asia, and also affects people of Mediterranean, North African, Middle Eastern, Indian and Asian origin.
Unlike alpha genes, there are only two beta genes, one each on chromosome 11.
Beta thalassaemia can range from moderate to severe. The most severe form of the condition is known as beta thalassaemia major (BTM), where both beta genes are affected. People with BTM will require blood transfusions for the rest of their life.
Beta thalassaemia intermedia (BTI) is the milder form of the condition, which is also known as non-transfusion-dependent thalassaemia (NTDT).
The symptoms of BTI will vary from person to person. Some people will experience symptoms of mild anaemia, while others will need blood transfusions.
Read more about the symptoms of thalassaemia.
These pages mainly focus on BTM, which is the most common and severe form of the condition in the UK.
What causes thalassaemia?
Thalassaemia is an inherited condition, which means it can be passed on to you from your parents.
It's not known exactly what causes the genetic mutations associated with thalassaemia. However, it's likely they've survived because carriers of the condition (both alpha and beta thalassaemia) are protected 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 is or has been a problem, including the Middle East, Asia, sub-Saharan Africa and certain Mediterranean countries such as Greece, Cyprus and Italy.
Read more about the causes of thalassaemia.
Thalassaemia can be diagnosed using a blood test. DNA tests may also be needed to determine the exact type of thalassaemia.
All pregnant women are offered screening for thalassaemia as part of antenatal screening.
Read more about how thalassaemia is diagnosed.
The only known cures for thalassaemia are a bone marrow transplant and cord blood transplantations, where blood cells are used from the umbilical cord of a newborn baby with parental consent. However, these procedures can cause a range of complications and aren't suitable for everyone.
One of the biggest problems with BTM is that it requires frequent blood transfusions, which can cause a build-up of iron in the body. This can result in serious health problems.
People receiving regular blood transfusions for BTM must also have iron chelation therapy, which is a treatment to remove the excess iron from their body.
Read more about how thalassaemia is treated.
Living with BTM
Living with BTM can be challenging. You'll need to have regular check-ups to assess the risk of possible complications.
Complications of thalassaemia can include:
- an enlarged spleen – where the spleen has problems recycling red blood cells, making it grow larger
- hormone complications – including delayed puberty and restricted growth
- heart complications – such as an irregular or disturbed heartbeat (arrhythmia)
- liver complications – such as hepatitis (swelling of the liver) or an enlarged liver (fibrosis)
- bone complications – such as bone and joint pain and osteoporosis (where the bones become thin and brittle)
One of the symptoms of beta thalassaemia major is a swollen abdomen caused by an enlarged liver or spleen
Who is affected by thalassaemia?
In England, beta thalassaemia major (BTM) is thought to affect around 1,000 people, with an estimated 214,000 carriers.
It most commonly affects people of Cypriot, Indian, Pakistani, Bangladeshi and Chinese origin.
In the UK, 8 out of 10 babies born with BTM have parents of Indian, Pakistani or Bangladeshi ancestry.
Page last reviewed: 20/05/2014
Next review due: 20/05/2016