Alpha thalassemia

Alpha thalassemia is a condition that changes the way red blood cells are made. The structural change leads to an overall reduction in the amount of haemoglobin in the body's circulation. This means that not enough oxygen is carried around the body. Anaemia (a shortage of red blood cells), pale skin, jaundice, weakness, fatigue are most common. The more serious forms of the condition can lead to significant health complications.

The genetics of alpha thalassemia are complicated since there are two genes involved in the making of haemoglobin. There are 4 types of alpha thalassemia — {CARRIER.NAME} is type {TYPE.NUMBER}, also known as {TYPE.NAME}

  • Type 1 / Silent carrier — These are people with a single variation out of 4 possible variations. They have no symptoms.
  • Type 2 / Carrier — People with 2 variations out of the 4. These individuals are healthy, but may have changes detected on haematology testing, such as small red blood cells.
  • Type 3 / HbH disease — People with 3 variations out of the 4. These individuals of have variable symptoms of alpha thalassemia. Some will show no symptoms while others may have anaemia, jaundice, fatigue, enlarged liver and spleen, heart defects, bone deformities and pregnancy related issues, such as pre-eclampsia.
  • Type 4 / Haemoglobin Bart disease — People with all 4 variations. These individuals have a fatal form of alpha thalassemia. Unfortunately, most babies with this condition experience death in utero, are stillborn or die shortly after birth.
Quick facts about alpha thalassemia
Genes: HBA1, HBA2
Inheritance: Autosomal Recessive
Relevant resources for alpha thalassemia

A quick genetics rundown

As humans we have about 23,000 genes. These genes are like tiny instruction manuals that influence our health, growth and development. We inherit half of our genes from our biological mum and the other half from our biological dad. These genes are lined up on structures called chromosomes. Most of us have 23 pairs of chromosomes. The first 22 pairs are called autosomes and for the most part - these are the same among men and women. The 23rd pair determine our sex - two X chromosomes for a female and one X and one Y chromosome for males.

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How is alpha thalassemia inherited?

alpha thalassemia is known as an autosomal recessive condition. For autosomal recessive conditions, if a person has a variation in one copy of their gene, they are a carrier. This means that they are healthy because they also have a working copy of the gene. But, they can still pass their non-working copy to their child.

If the other parent also happens to be a carrier of the same gene, there is a 25% (1 in 4) chance that they both pass this gene variation on to their child — and as such, have a child affected by the disease.

If both parents are carriers of alpha thalassemia, there’s a one in four chance that their children could develop symptoms.
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What is carrier screening?

Carrier testing is like a checkup for your genes. It tests to see if you carry a gene variation that could cause a serious genetic disease in your child. Eugene offers an inclusive genetic carrier screening panel that includes alpha thalassemia, but there's a total 301 conditions that can be tested.

Eugene’s carrier test is a clinical grade test that can be done from the comfort of your own home — it’s just a saliva test. You're also paired with a genetic counsellor who provides mindful support and guidance every step of the way.

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Should parents screen for alpha thalassemia before or early in pregnancy?

The biggest benefit of screening for alpha thalassemia is that it can help future parents understand their reproductive risk so they can be ready and empowered to make more informed decisions. If neither partner are carriers, it provides reassurance and peace of mind that the risk of having a child with a genetic disease is low.

Since 90% of children that have a recessive genetic disease like alpha thalassemia had no previous family history of it, it often feels completely out of the blue for the parents. Getting screened is a way to know this risk in advance, which can help familes manage or even prevent the disease in the first place.

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