Sickle Cell Disorders (SCD) are a serious group of conditions which are inherited (genetic). It affects haemoglobin, which is a protein inside red blood cells which carries oxygen. With SCD, the inherited genes are faulty, causing them to make abnormal haemoglobin. This causes the red blood cells to go out of shape and become sickle-shaped (like a crescent moon) instead of their normal disc shape.
Sickle cell disorders can cause various problems as the misshapen blood cells cause blockages in small blood vessels, including severe pain (called a sickle cell painful crisis) and organ damage. In between the episodes of illness, people with SCD are likely to feel well. Sickle cell disorders are not contagious.
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In the UK, about 17,500 people have SCD. It is more common in people whose family origins are African, African Caribbean, Asian or Mediterranean. It is rare in people of North European origin. On average, 1 in 2,400 babies born in England have SCD, but rates are much higher in some areas – about 1 in 300 in some places. SCD is now one of the most common inherited (genetic) conditions in babies born in the UK.
The most common type of SCD is where you have two sickle cell genes (sickle cell anaemia). The medical shorthand for this is haemoglobin SS or HbSS. Other types of SCD involve one sickle cell gene plus another unusual haemoglobin gene of a different type. These include: haemoglobin SC; haemoglobin S/beta thalassaemia; haemoglobin S/Lepore; haemoglobin SO Arab. The symptoms, diagnosis and treatment are similar for all the sickle cell conditions.
The cause is inherited (genetic). It is a change in the genes which tell the body how to make an important protein called haemoglobin. To get SCD, you need to have two altered haemoglobin genes, one from each parent. If you only have one of these genes, you will have sickle cell trait, which is very much milder.
Sickle cell genes affect the production of an important chemical called haemoglobin. Haemoglobin is located in red blood cells, which are part of the blood. Haemoglobin carries oxygen and gives blood its red colour.
The sickle cell genes make the body produce abnormal haemoglobin called HbS (normal haemoglobin is called HbA). HbS behaves differently from HbA. Under certain conditions, HbS makes the red blood cells change shape – instead of the normal doughnut shape, they become sickle-shaped, like a crescent moon. This is called sickling. Conditions which trigger sickling are cold weather conditions, infection, lack of fluid in the body (dehydration), low oxygen, and acid (acid is produced in hard physical exercise).
People who inherit the sickle cell trait have inherited one sickle cell gene from one of their parents. The other gene they have inherited is normal. As these individuals can make normal haemoglobin, their red cells do not have the same tendency to go out of shape as people with sickle cell disorders.
Sickle cell trait does not cause anaemia or painful crisis. Their general health is unlikely to be affected by the gene that they carry, apart from very rarely in extreme conditions which affect the amount of oxygen in your body (such as extreme exercise, dehydration or when going under a general anaesthetic). People with sickle cell trait can live a normal and healthy life. It is however important to know that their carrier status will remain the same for life.
The patient should inform all medical/dental staff of their carrier status before they receive any medical treatment to prevent unnecessary blood tests.
More information can be found here Sickle Cell Trait – Hematology.org
If a patient is a known carrier of the sickle cell gene and are planning on having a baby and their partner does not know whether they are a carrier of the sickle cell gene or another unusual haemoglobin, we recommend the partner gets a haemoglobinopathy screening test done. This is a free test which can be organised via the GP surgery.
If the partner is found to also carry the gene for sickle cell disorders or another unusual haemoglobin, then the GP can refer the patients to a genetic counsellor, who can explain the risks to their children and what their options are.
