Thalassaemia

Thalassaemia is the name given to a group of hereditary red blood cell disorders that affect haemoglobin production. Thalassaemias are among the most common inherited disorders in the world: the affect more than 300,000 children worldwide, particularly in areas where malaria is common, including the Mediterranean and Middle East regions, Sub-Saharan Africa, the Indian subcontinent and Southeast Asia.

Causes and types

Haemoglobin is a very important component in red blood cells, as it carries oxygen around the body. Haemoglobin is comprised of four sub-units: two alpha-globin sub-units (alpha1 and alpha2) and two beta-globin sub-units (beta1 and beta2). These components are created by specific genes that are passed onto the child from each parent. Sometimes genes can become mutated or deleted and therefore do not allow the regular production of haemoglobin. This leads to red blood cells that are poorly formed, with a shortened life span, anaemia and a lack of oxygen transported to all parts of the body.

Healthy red blood cells use haemoglobin to carry oxygen. 

Thalassaemia is a hereditary condition caused by gene mutations or deletions that are passed on from your mother or father, or both. An estimated 5% of the world's population carries one of these mutations.Depending on the number and type of mutated genes or deleted genes, varying types of thalassaemia are caused.

Alpha thalassaemia

Alpha thalassaemia involves the deletion of between one and four of the genes required to make alpha-globin.

Alpha thalassaemia carrier

Of the four possible genes used for making alpha-globin, a person has either one or two deleted genes, but is healthy. These people are called 'carriers' and they have a risk of giving birth to a child affected with either haemoglobin H disease or Bart's hydrops fetalis (see below) if their partner is also a carrier.

Haemoglobin H disease

Of the four possible genes used for making alpha-globin, individuals have three deleted genes and require regular medical care. This can include mild to moderate anaemia that requires lifelong treatment with intermittent blood transfusion.

Bart's hydrops fetalis

None of the four genes needed to make alpha-globin are present. This means that haemoglobin cannot be formed and oxygen cannot be transported around the body. This often results in death before birth.

Beta thalassaemia

Beta thalassaemia involves the mutation of one or two of the genes needed to make beta-globin. There are two forms of beta thalassaemia.

Beta thalassaemia minor

People with beta thalassaemia minor have a mutation in one gene used for making beta-globin. These individuals are healthy and are called carriers. If you have Beta thalassemia minor and your partner is also a carrier, there is a risk of having a child affected beta thalassaemia major. There is a risk of having a child affected with beta thalassaemia major if their partner is also a carrier.

Beta thalassaemia major

Individuals with beta thalassaemia major have mutations in both genes used for making beta-globin. This results in severe anaemia that requires lifelong treatment.

Signs and symptoms

Signs and symptoms associated with thalassaemia can include:

• Weakness;
• Fatigue;
• Jaundice;
• Enlargement of organs, especially the spleen;
• Slow growth;
• Failure to thrive;
• Paleness;
• Dark urine;
• Abdominal swelling, and;
• Deformities of facial bones.

Methods for diagnosis

Thalassaemia is diagnosed by several tests involving the components of your blood.

Full blood examination

This is a simple blood test that examines the red blood cells and other components of blood. Thalassaemia may be suspected if there are specific changes in the number, size, shape and colour of red blood cells.

Haemoglobin electrophoresis

This test measures the amounts of different forms of haemoglobin in blood. This test can be used to detect most carriers.

DNA analysis

This test can identify which mutations or deletions of haemoglobin genes a person has. This can also be used to detect or confirm carriers.

Types of treatment

The treatment of thalassaemia depends on the type and severity of the condition. No treatment is required for carriers of alpha thalassaemia or beta thalassaemia minor. Haemoglobin H disease and beta thalassaemia major are treated with regular blood transfusions. This is done to boost the levels of red blood cells and, most importantly, haemoglobin. Over time, the red blood cells 'wear out' and a new blood transfusion is required. This is an ongoing condition and transfusions will be required for life.

In some cases, bone marrow transplants are also possible and can sometimes result in cure. If successful, the new bone marrow can produce normal blood cells with normal haemoglobin. However, there are significant risks with this procedure, including the possibility of death. Because people with thalassaemia can lead normal lives with intermittent blood transfusions, bone marrow transplant may not be considered.

A blood transfusion. 

Potential complications

Complications associated with thalassaemia can include passing on the condition to a child, if both parents have the condition or are carriers of the condition.

For people requiring regular blood transfusions, there is a side effect of increased iron accumulating in the body. Over time this becomes stored in the liver, heart and pancreas and can lead to liver cirrhosis, heart failure and diabetes. Excess iron can be removed using medications, such as desferrioxamine, in a process called iron chelation.

Thalassaemia can cause bone deformities. This occurs because thalassaemia causes an expansion of bone marrow, leading to a widening of bones. This can make bones brittle and can cause facial bone structure deformities and slow growth rates in children.

Thalassaemia can also cause your spleen to enlarge (splenomegaly). This occurs because your spleen must work harder to filter and remove damaged blood cells. Sometimes the spleen can become too large and must be removed.

Prognosis

Depending on the type of thalassaemia, dealing with the condition can be difficult. If you are a carrier, no treatment is required, but there is a risk of having a child with thalassaemia if your partner is also a carrier. If you have a more severe form of thalassaemia, regular blood transfusions will be required for life. A good network of family and friends can support you with this condition.

Prevention

If you are planning on having a baby, screening is possible to identify if you or your partner are carriers of thalassaemia. Screening is particularly important if there is a family history of the condition. This can identify if there is a chance that you will have a child with thalassaemia.