Beta Thalassaemia

Most of our physical characteristics are inherited through the genes we take from our parents; for example, the shape of our nose, the colour of our skin and eyes. We also inherit our haemoglobin (Hb) type from our parents, through the genes.

Haemoglobin (Hb) is the substance in the blood which gives it its red colour. It carries the oxygen we breathe in through our nose to all our body parts; oxygen is vital for maintaining life. Without red blood cells, the body cannot carry oxygen and without oxygen the body cannot live, see Haemoglobin .

The usual and most common adult haemoglobin type is called Haemoglobin A and contains two chains called BETA (β) and ALPHA (α).Alpha (α) chains are essential for making a number of haemoglobins including Fetal (F), Adult (A) and minor adult Haemoglobin (A2), see Haemoglobin , all these need two alpha chains.

The amount and quality of beta and alpha chains a person makes is controlled by the haemoglobin gene they inherit from their parents.

Where a person has inherited haemoglobin A from both parent they will have TWO usual beta genes (βAβA), one from each parent, and Two PAIRS of alpha genes one pair from each parent (αα/αα), (see Diagram 1)

 Inheritance of alpha chains
Diagram 1: Normal

Some people inherit one usual haemoglobin A gene and one unusual Beta Thalassaemia gene, in which case they have a condition known as Beta Thalassaemia trait, (Hb AβThal), often referred to as Beta Thalassaemia ‘minor’ or a ‘carrier’, this is a defect of the beta globin gene and affects the beta chain, see Haemoglobin .

Some people do not inherit the usual number of Alpha genes in which case they will have a Alpha Thalassaemia trait, this is a defect of the alpha globin gene and affects the alpha chain, see Haemoglobin .

The information here is about BETA THALASSAEMIA only; for information about Alpha Thalassaemia, see Alpha Thalassaemia.

Beta Thalassaemia Trait (Carrier)

Beta Thalassaemia trait occurs when an individual inherits one usual Beta gene from one parent and one unusual Beta Thalassaemia gene from the other (Hb AβThal). It is mostly found in areas of the world where malaria is, or was common particularly the Mediterranean, Asia, and Far Eastern countries, it is also found less commonly in people of African and Caribbean descent. Because of migration and intermarriage it is seen in other areas of the world occasionally for example in white Northern Europeans.

It is estimated that approximately:

  • 1 in every 7 Greek Cypriots have Beta Thalassaemia trait
  • 1 in every 12 Turks have Beta Thalassaemia trait
  • 1 in every 20 Asians have Beta Thalassaemia trait
  • 1 in every 20-50 Africans/African-Caribbeans have Beta Thalassaemia trait
  • 1 in every 1000 White English have Beta Thalassaemia trait

People with beta Thalassaemia trait have red blood cells which are slightly smaller, paler, and have less red pigment, but this does not cause any health problems. Generally, their red blood cells are still able to carry oxygen around the body as efficiently as someone with the two usual beta genes. Because these individuals are healthy they will not know that they are carrying this unusual haemoglobin, unless they have a special blood test.

The blood of people who have beta Thalassaemia trait has a slightly lower level of iron. However they do not need to take iron medicines, unless special blood tests have shown that they are lacking in iron and a doctor advises this treatment.

If a couple BOTH have beta Thalassaemia trait, EACH time they are expecting a child there is a 1 in 4 chance that their child could inherit a serious blood disease called Beta Thalassaemia Major for examples of how the inheritance works see Inheritance of Haemoglobin.

Beta Thalassaemia Intermedia

There is a variety of beta Thalassaemia genetic mutations, the milder forms known as beta plus result in the production of a small amount of beta chains β+Thal whilst the more serious types known as beta zero Thalassaemia result in no production of beta chains β0Thal.

Beta Thalassaemia intermedia occurs when a person has inherited the milder forms of the beta plus globin gene defect from both parents (β+Thal β+Thal) and no normal adult Haemoglobin A or they have inherited a beta plus gene defect with another unusual haemoglobin such as haemoglobin (Eβ+Thal) and no normal adult Haemoglobin A. In these cases the individual is able to produce a small amount of beta globin chains.

The severity of this condition depends on the nature of the beta Thalassaemia gene that has been inherited and how it affects the production of the beta chain.

Many individuals with beta thalassaemia intermedia are mildly or moderately affected and may not need blood transfusion whilst others are seriously affected and need similar care to those with beta Thalassaemia major which is described below.

Beta Thalassaemia Major

Beta Thalassaemia Major is a serious anaemia affecting people who have inherit two Beta Zero Thalassaemia genes (β0Thal β0Thal) one from each parent.

People with Beta Thalassaemia major do not produce enough healthy, mature red blood cells; their red blood cells do not mature enough to work effectively, does not survive the pressures they go though in the blood circulation, the cells get damaged very easily and do not live long enough. Therefore, these individuals become very anaemic. Without enough red blood cells to carry oxygen around the body a person cannot survive because oxygen is vital for life.

From about the age of 3 months children with this condition become very pale, lethargic, lose their appetite, have repeated episodes of diarrhoea and vomiting and are prone to picking up infections; they then fail to fail to grow and thrive; if untreated they usually do not survive early childhood. But with proper medical care they can grow up, reach adulthood, have children and achieve as much as anyone else.

Treatment of Beta Thalassaemia Major

A person born with the serious form of this condition will need blood transfusion about every four to six weeks and throughout their adult life.

There is no simple cure for Beta Thalassaemia Major. Although bone marrow transplantation can cure the condition, there is a need to find a matching donor, complications can occur as a result of the procedure and the rate of success is unpredictable.

Although this condition is called anaemia, it is not caused by lack of IRON. Individuals are still able to take in iron from the food they eat, this, combined with the iron in the blood they are given during blood transfusion means that too much iron builds up in the body. This excess iron can cause serious damage to body organs such as the heart, liver and pancreas leading to serious life threatening complications.

To get rid of the excess iron, people with Beta Thalassaemia Major need to inject themselves with a special drug called Desferal. Treatment is monitored and adjusted according to the individual’s needs. An oral medication (Exjade) which helps to get rid of excess iron from the body is now available but it is not suitable for everyone. With good medical care, family support and encouragement, people with beta Thalassaemia major are able to live well and cope with their condition.

Difference between Beta Thalassaemia Trait and Major

Beta Thalassaemia trait cannot change into a disease because it is inherited whatever a person has inherited from their parents is what they will have all their life. Apart from a very mild anaemia it does not affect the individual however it becomes important when the individual is considering having children, because the child may inherit this unusual haemoglobin gene. And if the other parent also has this or another significant unusual haemoglobin gene their child could inherit beta Thalassaemia major or beta Thalassaemia intermedia or any other unusual haemoglobin gene combination.

Beta Thalassaemia major (disease) however is a serious blood condition. Individuals with this condition are unable to make enough healthy, mature red blood cells and depend on blood transfusions and other medical treatments all their life.

Inheritance of Beta Thalassaemia

A person can only get beta Thalassaemia trait or beta Thalassaemia intermedia or beta Thalassaemia major from their parents. These conditions CANNOT be transmitted like an infection; they can only be inherited through the genes.

If both parents have beta Thalassaemia trait each time they are expecting a child there is a 1 in 4 chance that the child could inherit the usual number of beta genes, a 2 in 4 chance the child could inherit Beta Thalassaemia trait and a 1 in 4 chance the child could inherit Beta Thalassaemia Major, see Inheritance of Haemoglobin.

If a couple both have Beta Thalassaemia Trait and they want to have a Baby

Where a couple have beta Thalassaemia trait they have the following options open to them if they want to have children:

  • ignore the information, get pregnant the usual way and let nature take it course
  • have the baby tested in the womb in early pregnancy
  • adopt a child
  • use a donor egg or sperm and have In Vitro Fertilisation (IVF)

Testing the baby in the womb is called prenatal diagnosis and can be done as early as ten weeks of pregnancy in most cases. The test is usually done in a special clinic in a hospital and depending on the type of test that the woman / couple are offered the result is usually available within a few days, but can take up to two weeks. The couple can also obtain a copy of the leaflet which explains prenatal diagnosis from the Brent Sickle Cell & Thalassaemia Centre.

It is advisable for an individual or couple to discuss the various options that are available with a GP, Midwife, hospital doctor, genetic counsellor or a specialist nurse at the specialist Centre. They will be able to provide more information, advice, and support to help them reach a decision that is best for them.

The Family Connection

Once Beta Thalassaemia or any other unusual haemoglobin gene has been found in one family member it is important to be aware that other members of the same family may also have the unusual haemoglobin gene. Therefore, it is important to share the information with other family members especially with those who are of child bearing age, planning to get married, start a family or have more children - brother, sisters, aunts, uncles, cousins.

Testing for Beta Thalassaemia

Anyone who wants to be tested to find out which haemoglobin they have inherited from their parents can visit their GP or contact their local specialist National Sickle Cell / Thalassaemia Centre.