Sickle cell anaemia - Causes 

Causes of sickle cell anaemia 

If you have sickle cell anaemia, your blood cells can get stuck when moving through small blood vessels, stopping the supply of oxygen to parts of your body.

Sickle cell anaemia is caused by a genetic mutation that affects the normal development of haemoglobin.

A genetic mutation is a permanent change in the normal pattern of genetic information inside all living cells. This results in one or more of the processes of the body not working as they should.


Haemoglobin is a substance found in red blood cells which acts as a sort of transport mechanism for your blood.

As blood passes through your lungs, the haemoglobin pulls in oxygen while at the same time releasing carbon dioxide. This process is known as oxygenation. 

After moving away from your lungs, the haemoglobin delivers oxygen to the body’s tissue and removes excess carbon dioxide to take back to your lungs. This process is called deoxygenation.

During deoxygenation, healthy haemoglobin molecules should smoothly rearrange themselves into a different shape. In cases of sickle cell anaemia, the smooth rearrangement does not occur due to the mutated gene.

Instead, the haemoglobin inside blood cells clumps together into solid structures. The clumping distorts the normal shape of the red blood cells, causing them to take on a characteristic rigid, sickle shape.

The genetics of sickle cell anaemia

Genes come in pairs. You receive one copy of a gene from your mother and one copy from your father.

To develop sickle cell anaemia you would need a pair of the mutated genes; one from your mother and one from your father.

If you only receive one copy, you will not develop sickle cell anaemia, but you will be a carrier of the sickle cell gene. This is often referred to as having the sickle cell trait. It is estimated that 1 in 10 people of African or Caribbean descent has this trait.

If you are a carrier, you will not usually notice any obvious symptoms unless you are in an low oxygen environment, such as on top of a mountain.

If both you and your partner have the sickle cell trait, there is a risk that any children you conceive will inherit a pair of mutated genes and develop sickle cell anaemia. The chances of sickle cell anaemia being passed on are outlined below:

  • There is a one in four chance your baby will receive a pair of normal haemoglobin genes.
  • There is a one in two chance that your baby will receive one normal gene and one mutated gene. In this case, they will not have sickle cell anaemia, but they will carry the sickle cell trait.
  • There is a one in four chance that your baby will receive a pair of mutated genes. This means that they will have sickle cell anaemia.

If one parent has the sickle cell trait and the other parent has normal haemoglobin, the baby will not develop sickle cell anaemia. However, there is a one in two chance that the baby will receive the sickle cell trait.

Finally if you have ‘full-blown’ sickle cell anaemia and your partner has the sickle cell trait, any baby you have has a one in two chance of developing sickle cell anaemia.

This is because it is certain that they will receive a mutated gene from you and there is a one in two chance that they will receive a mutated gene from your partner.

Read more about genetics.

Page last reviewed: 28/02/2012

Next review due: 28/02/2014


How helpful is this page?

Average rating

Based on 45 ratings

All ratings

Add your rating


Find and choose services for Sickle cell anaemia