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Sickle cell disorder

 


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Condition
Sickle cell disorder
Class
Blood
Description
Sickle cell disorder is the name of a group of inherited conditions that affect the red blood cells. The disorder gets its name from the elongated, pointed appearance of the red blood cells that resemble a farmer’s sickle.

The most common and severe form of the disorder is sickle cell anaemia. In this condition, the deformed red blood cells have difficulty in passing through narrow blood vessels, causing a blockage and cutting off the blood supply to the area of the body affected. This causes attacks of severe pain, damages vital organs and reduces life-expectancy.

Other less severe forms of sickle cell disorder include sickle cell trait, haemoglobin SC disease and sickle beta thalassaemia.

The different types of sickle cell disorder are found mainly in families that originate from Africa, the Middle East, the Eastern Mediterranean and the Caribbean. In the UK, it is estimated that there are over 12,000 adults and children with sickle cell disorder, mostly among people of African or Caribbean descent.
Causes
Sickle cell disorder is inherited and occurs through a change or mutation in the gene that carries the instruction to make haemoglobin, a protein contained within the red blood cells that is responsible for carrying oxygen to all parts of the body. The gene mutation causes the production of sickle haemoglobin instead of normal haemoglobin.

There are many types of haemoglobin, but the most common is haemoglobin A or HbA. Most children inherit a gene for this type of haemoglobin from both parents. In such cases, this is represented by HbAA.

If a child inherits a mutated gene that carries the instruction to make sickle haemoglobin (HbS) from both parents, represented by HbSS, that child will develop sickle cell anaemia.

If a child inherits a mutated gene that carries the instruction to make sickle haemoglobin (HbS) from one parent, and a gene for normal haemoglobin from the other parent, represented by HbAS, that child will have what is known as sickle cell trait. Here, the person affected will not develop the symptoms of sickle cell anaemia unless exposed to situations where there is a shortage of oxygen, for example when climbing at high altitudes.

In haemoglobin SC disease and sickle beta thalassaemia, the child has inherited a gene for producing sickle haemoglobin and a gene for producing another type of haemoglobin called haemoglobin C or beta thalassaemia. In both these cases, people affected have a milder form of sickle cell disorder and symptoms are less severe than those of sickle cell anaemia.

Sickle haemoglobin, in all forms of sickle cell disorder, behaves differently from normal haemoglobin. When oxygen levels in the blood are low, molecules of sickle haemoglobin in the red blood cells stick together, distorting the red blood cells from their normal, flexible doughnut shape into their less flexible sickle shape. The less flexible red blood cells have difficulty passing through very narrow blood vessels, causing blockages and depriving the areas affected of oxygen. Also, repeated changes from doughnut to sickle shape damages the outer covering or membrane of the red blood cells, greatly reducing their normal 100-120 days lifespan. As the levels of red blood cells fall, anaemia develops.
Symptoms
Although sickle cell disorders are present from birth (because it is an inherited disorder), symptoms are rare before the age of 3-6 months, due to the persistence of foetal haemoglobin (HbF) which provides adequate oxygen to the body. First symptoms to appear may be jaundice, a painful swelling of the hands and feet and an enlarged spleen. Children with sickle cell disorder are also extremely susceptible to infections such as meningitis and septicaemia. Strokes (blood clots in the blood vessels to the brain) are another devastating complication. While they are rare in children generally, strokes are potentially one of the common causes of disability in a child with sickle cell disorder. During pregnancy, women with sickle cell disorder are at increased risk of pre-eclampsia and premature labour, which can be life-threatening for the mother and her unborn baby.

At most times, people with sickle disorder appear and feel quite well. However, certain trigger factors such as dehydration, low oxygen levels, fever, infection, exposure to cold or becoming pregnant may cause symptoms suddenly to appear. These sudden attacks are known as sickle cell crises. They occur at different times in different people, some getting crises frequently, others getting a crisis only once every few years. The severity of symptoms also varies between attacks and between individuals.

The main symptoms of sickle cell disorders are pain, anaemia and infection. Pain is caused by blockage of blood vessels by the sickled red blood cells. Consequently, pain can occur in any part of the body where blood vessels are liable to become blocked, but most frequently occurs in the chest, back, limbs, jaw and abdomen. In some cases, pain is so severe that the person affected will need to be admitted to hospital. If the blood supply to certain vital organs such as the liver, kidneys or brain is affected, these organs will be damaged resulting in liver or kidney failure or strokes.

Anaemia, arising through the shortened lifespan of the sickled red blood cell, is another common problem. Symptoms include fatigue, shortness of breath and a low exercise capacity. In extreme cases of anaemia, blood transfusions may be required.

People with a sickle cell disorder are particularly prone to minor infections and to life-threatening infections such as septicaemia, pneumococcal meningitis and osteomyelitis.
Treatment

There is no cure for sickle cell disorders. Treatment is aimed at reducing the number and severity of sickle cell crises. The only treatment approved to decrease the frequency and severity of crises is a drug called hydroxyurea, but this is only partially effective in most people and ineffective in others, and caries the risk of causing serious side effects.

When a sickle cell crisis does occur, treatment is aimed at controlling pain, correcting anaemia and stopping infections. If complications develop, treatment is aimed at managing the complications and the area of the body affected.

When to see your pharmacist

Talk to your pharmacist if you want information about sickle cell disorder. Your pharmacist will be able to explain the condition to you and will be able to refer you to others for more specific advice if required.

When to see your doctor

If you are of African, Middle Eastern, Eastern Mediterranean or Caribbean descent, if you have other family members affected by sickle cell disorder, or if you think that you may have sickle cell disorder see your doctor. Your doctor will arrange for you to have a blood test to determine if you have the disorder or sickle cell trait. Ante-natal screening can also be performed to assess unborn babies. Screening tests should also be conducted before having an operation involving a general anaesthetic.

If the screening tests show that you or your baby has sickle cell disorder or sickle cell trait your doctor will advise counselling to ensure that you fully understand the condition.

Living with sickle cell disorder

Maintaining a good general state of health and eating a healthy diet will help reduce the number of sickle cell crises. Make sure that you eat plenty of fresh green vegetables. These are a good source of folic acid that will help produce red blood cells and reduce the chances of anaemia. Do not smoke and drink alcohol only in moderation.

Take regular exercise but avoid over-exertion and try to keep warm. If swimming, do not stay in the water until you get cold. Wrap up warmly when you get out.

Avoid situations that have caused crises before. In particular, be careful when at higher altitudes as low oxygen levels may trigger an attack. Keep your fluid levels up, drink plenty of water especially if you have been perspiring because of exercise or hot weather.

Infections should be treated promptly and immunisations against infectious diseases should be kept up to date. If your doctor has recommended that you take antibiotics to reduce the risk of infection, make sure that you take them every day. If you plan to travel abroad, make sure that you allow sufficient time before you travel for any additional vaccinations that you will need to protect against diseases such as hepatitis A and hepatitis B in the countries that you are visiting. If there is a risk of malaria in the country, make sure that you take the recommended anti-malarial medicines before, during and after your holiday.

Keep a supply of analgesics, appropriate to the age of the person with sickle cell disorder, to be able to treat pain promptly if a crisis does develop.

Maintain regular visits to your doctor or specialist to ensure that medical checks and blood tests are performed regularly, to help reduce crises or to manage them more effectively when they occur.

If your child is affected, inform the school and make sure the teachers understand how the condition may affect your child and they know what to do in the event of a crisis.

Further information

The Sickle Cell Society provides information, counselling and caring for those with sickle cell disorder, their families and carers.

Sickle Cell Society
54 Station Road
London
NW10 4UA
Tel: 020 8961 7795
Email: info@ sicklecellsociety.org
www.sicklecellsociety.org



Action Medical Research, the leading UK-wide medical research charity dedicated to helping babies and children.

Action Medical Research
Vincent House
North Parade
Horsham
West Sussex
RH12 2DP
Tel: 01403 210406
www.action.org.uk



Reviewed on 27 June 2011


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