Sickle-cell anaemia

Sickle cell anaemia is a serious inherited blood disorder where the red blood cells, which carry oxygen around the body, develop abnormally.

The disorder mainly affects people of African, Caribbean, Middle Eastern, Eastern Mediterranean and Asian origin. In the UK, sickle cell disorders are most commonly seen in African and Caribbean people.

Normal red blood cells are flexible and disc-shaped, but in sickle cell anaemia they can can become rigid and shaped like a crescent (or sickle).

The sickle-shaped cells contain defective haemoglobin, the iron-rich protein that enables red blood cells to carry oxygen from your lungs to the rest of the body.

The abnormal cells are also unable to move around as easily as normal shaped cells and can block blood vessels, resulting in tissue and organ damage and episodes of severe pain.

Such episodes are known as a sickle cell crisis or a vaso-occlusive crisis. They can last from a few minutes to several months, although on average most last five to seven days.

The abnormal blood cells also have a shorter lifespan and aren't replaced as quickly as normal blood cells. This leads to a shortage of red blood cells, known as anaemia.

Symptoms of anaemia include lethargy (a lack of energy), tiredness and breathlessness, particularly after exercise.

Read more about the symptoms of sickle cell anaemia.

What causes sickle cell anaemia?

Sickle cell anaemia is caused by a mutation (an abnormal change) in the gene that instructs the body to produce haemoglobin.

The sickle cell gene is inherited (passed on between family members). To get sickle cell anaemia you have to inherit the defective gene from both parents.

If you only inherit the gene from one parent, you have what's known as the sickle cell trait. It's likely that your blood will contain some sickle cells, but you'll be able to produce normal haemoglobin and won't usually experience symptoms. However, you'll be a carrier of sickle cell anaemia and may pass the abnormal gene on to your children.

In England, about 250,000 people are thought to have the sickle cell trait, with those of African-Caribbean origin primarily affected.

If two people with the sickle cell trait have a child, there's a one in four chance that the child will be born with sickle cell anaemia.

Read more about the causes of sickle cell anaemia.

Diagnosing and screening for sickle cell anaemia

Sickle cell anaemia can be diagnosed using a blood test. The blood is checked for defective haemoglobin.

A small level of defective haemoglobin would indicate that a person has the sickle cell trait but not sickle cell anaemia. A high level would indicate sickle cell anaemia.

Antenatal screening (screening carried out during pregnancy) is used to check for inherited disorders, such as sickle cell anaemia.

Antenatal screening for the sickle cell trait is available in areas where the condition is most common, such as where there are large Afro-Caribbean communities.

In parts of the country where sickle cell anaemia is uncommon, a questionnaire that focuses on family origin is used to assess the risk of sickle cell disorders.

All babies born in the UK are tested for sickle cell anaemia as part of the heel prick newborn screening test that's carried out by the midwife.

People in high risk groups should be tested for the sickle cell trait or thalassaemia (see box) before having a general anaesthetic. This is because this type of anaesthesia temporarily lowers the amount of oxygen in the blood, which could be dangerous for someone with these blood conditions.

Treating sickle cell anaemia

If your child is diagnosed with sickle cell anaemia, they'll be referred to a specialist sickle cell centre.

Sickle cell centres are specialist units usually based in large hospitals. The staff at these units have a high level of expertise in treating people with sickle cell anaemia.

A detailed plan outlining future medical care will be drawn up and you'll be given information and support to help manage your child’s condition.

Following simple lifestyle advice, such as drinking plenty of fluids, can help reduce the risk of experiencing a sickle cell crisis. Read more self care advice.

Sometimes, a person with sickle cell anaemia will continue to experience pain despite taking preventative measures. In such cases, a medication called hydroxycarbamide may be recommended.

Read more about how sickle cell anaemia is treated.

Complications of sickle cell anaemia

The symptoms of sickle cell anaemia can have a significant impact on a person's quality of life. If complications develop, these can be very serious. Possible complications include:

stroke – where the blood supply to part of the brain is cut off
increased vulnerability to infection
acute chest syndrome – where the lungs suddenly lose their ability to breathe in oxygen (often the result of an infection)
pulmonary hypertension – where the blood pressure inside the blood vessels that connect the heart to the lungs becomes dangerously high

However, following improvements in preventative treatment, many complications associated with sickle cell anaemia can be avoided.

The life expectancy of a person with sickle cell disease has increased significantly over recent decades. A person with the condition can expect to live into their late 40s or early 50s.

Read more about the complications of sickle cell anaemia.

When to seek urgent medical advice

Because of the risk of potentially life-threatening complications, it's important to look out for any signs or symptoms that the health of a person with sickle cell anaemia has suddenly deteriorated. These include:

a high temperature (fever) of 38C (100.4F) or above
breathing difficulties
severe pain that develops during a sickle cell crisis that can't be controlled using over-the-counter painkillers, such as paracetamol or ibuprofen

Read more about when to seek urgent medical advice.

Blood: Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Blood vessels: Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.
Bone marrow: Bone marrow is the soft, spongy tissue in the centre of bones that produces blood cells.
Disease: A disease is an illness or condition that interferes with normal body functions.
Genetic: Genetic is a term that refers to genes, the characteristics inherited from a family member.
Lungs: Lungs are a pair of organs in the chest that control breathing. They remove carbon dioxide from the blood and replace it with oxygen.
Oxygen: Oxygen is an odourless, colourless gas that makes up about 20% of the air we breathe.
Pain: Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.
Tissue: Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.