Thalassaemia

Thalassaemia is the most common inherited blood condition in the world. It is caused by changes to the genes that direct the body to make haemoglobin, the protein in red blood cells that carries oxygen around the body.

How thalassaemia affects haemoglobin#

Thalassaemia can affect people of any background, although it is more common in some populations, including people of Mediterranean ancestry and across a broad region extending through India, the Middle East, Asia and parts of Latin America. Thalassaemia major is usually diagnosed within the first six months of life and can be fatal in early childhood without ongoing treatment.

There are two main types: alpha-thalassaemia and beta-thalassaemia. Alpha-thalassaemia involves changes in the alpha-globin genes (HBA1 and HBA2). Beta-thalassaemia involves changes in the beta-globin gene (HBB).

Thalassaemia minor (carriers)#

A person has thalassaemia minor when they carry a genetic change in only one copy of the relevant gene while keeping a working second copy. For example, someone with beta-thalassaemia minor has one changed copy of the HBB gene and one unchanged copy.

Because they still have a functioning copy of the gene, carriers usually have mild or no symptoms. However, they carry the genetic change and can pass it on to their children. The only way to find out whether someone is a carrier is a specific blood test for thalassaemia. The World Health Organization estimates that around 5 to 7 per cent of the world’s population has thalassaemia minor.

Thalassaemia major#

Thalassaemia major occurs when a person has changes in both copies of the affected gene or genes, so they have no fully functioning copy. People with alpha- or beta-thalassaemia major develop symptoms of the condition, and beta-thalassaemia major is more common than alpha-thalassaemia major.

When both parents carry the same type of thalassaemia, each pregnancy carries a:

• 25 per cent chance of the child inheriting the changed gene from both parents and developing thalassaemia major
• 50 per cent chance of inheriting the changed gene from one parent and becoming a carrier
• 25 per cent chance of not inheriting the changed gene at all

The red blood cells of a person with thalassaemia major survive only a few weeks, compared with around four months for typical red blood cells. The resulting lack of haemoglobin reduces the oxygen supply to every cell in the body.

Symptoms appear in early childhood#

Symptoms of thalassaemia major can include:

• severe anaemia, because red blood cells are made without enough haemoglobin to carry oxygen
• paleness
• enlargement of organs such as the spleen and liver
• sleep difficulties
• poor appetite
• failure to grow and thrive

Treatment must continue for life#

There is no cure for thalassaemia major and treatment continues for life. Ongoing care includes regular blood transfusions to keep haemoglobin levels up.

Over time, repeated transfusions can lead to a build-up of iron in the body, which can cause serious problems including diabetes, heart failure and liver disease.

Iron-chelation medication#

Medications called iron chelators are used to remove excess iron. They work by binding to the iron so it can be cleared from the body. Chelators may be taken by mouth or given by injection.

How thalassaemia is diagnosed#

Thalassaemia can be diagnosed through:

• blood tests, including a full blood count to measure the amount of haemoglobin and the different kinds of blood cells, and a test that measures the types of haemoglobin present
• genetic testing

Testing before pregnancy#

It is generally recommended that couples thought to be at risk are tested for carrier status, ideally before starting a family. Testing can usually be arranged through your doctor. If you are already pregnant, talk to your doctor about options for testing during pregnancy.

Options for couples who are both carriers#

Couples who are both carriers have several choices. Some decide not to have biological children and consider adoption, fostering, or using donor sperm or eggs. Others accept the chance of having a child with thalassaemia major. Couples may also choose prenatal diagnosis, with the option of ending the pregnancy if the fetus is diagnosed with thalassaemia major.

Pre-implantation genetic diagnosis (PGD) is another option. This uses assisted reproductive technology to create an embryo that can be tested for thalassaemia before being transferred to the uterus.

Bone marrow transplants#

A bone marrow transplant is currently the only chance of a cure for thalassaemia major, but the risks are considerable. The odds of finding a compatible donor are limited, and most donors are siblings. The operation is more successful in young children who do not have iron overload, but graft rejection or even death can still occur. These risks mean transplantation is not a viable option for some families.

It is worth remembering that a person with thalassaemia major can live a full life with regular transfusions and medication, and genetic research is continuing in the hope of finding a cure.

Genetic counselling#

If your child or another family member has been diagnosed with thalassaemia, or if it runs in your family, it can help to speak with a genetic counsellor.

Genetic counsellors are health professionals qualified in both counselling and genetics. As well as offering emotional support, they can help you understand what thalassaemia is, what causes it, how it is inherited, and what a diagnosis means for your child’s health and development. They are trained to provide information and support that is sensitive to your family circumstances, culture and beliefs.

If thalassaemia runs in your family, a genetic counsellor can explain the genetic testing options available to you and other family members. You may also choose to see a genetic counsellor when planning a family, to understand your risk of passing the condition on or to arrange prenatal testing.

Key points#

• Thalassaemia is the most common inherited blood condition in the world.
• It is caused by changes to the genes for haemoglobin, the protein that carries oxygen in red blood cells.
• Carriers (thalassaemia minor) usually have mild or no symptoms but can pass the condition on.
• Thalassaemia major causes severe anaemia and needs lifelong treatment with transfusions and iron-chelation medication.
• A person with thalassaemia major can live a full life with regular treatment.

Where to get help#