Sickle Cell Disease explained

Sickle-Cell Disease (SCD) is a hereditary disease of the red blood cells. The main job of red blood cells in the body is to carry oxygen. The protein in the red cell that carries oxygen is called haemoglobin. Persons with SCD inherit an abnormal haemoglobin gene from each parent, which results in the production of abnormal red blood cells.

Normal red cells are soft and round and can travel through the body without any problems. In persons with SCD, under certain conditions, red blood cells can become hard, sticky and curved in shape (like a banana). These red cells are called sickle cells. Sickle cells have a shortened lifespan and are destroyed rapidly in the circulation. They are also not very flexible, and may get stuck in small blood vessels. When this happens, some parts of the body do not get enough oxygen.

These features of the abnormal sickle red blood cell are what causes many of the problems, such as anaemia (weak blood), jaundice (yellow eyes), gallstones, bone pain, pneumonia, leg ulcers (sores), increased susceptibility to infection and strokes, that can occur in persons with SCD.

ARE THERE DIFFERENT TYPES OF SCD?

There are many forms of the disease (genotypes). If one inherits the abnormal sickle haemoglobin (Hb S) gene from both parents, the affected person has the most common as well as one of the most severe forms of the disease (Hb SS disease). If one inherits the sickle gene as well as the gene for another abnormal haemaglobin (eg Hb C or thalassemia), other forms of SCD may occur, such as Hb SC disease and sickle thalassemia.

Hb SS disease is often referred to as 'full blown', which can lead to the misconception that other forms of the disease are not important. On the contrary, whereas Hb SS disease is a severe form, it is NOT the only severe form of the disease, and even so-called MILD forms of the disease can have many problems.

In Jamaica, one in 150 persons is affected by some form of the disease.

DISEASE CARRIERS

Persons who have one normal haemoglobin (Hb A) gene and one sickle haemoglobin (Hb S) gene are said to be carriers of the disease. They have the sickle cell trait (Hb AS). Carriers usually have no signs or symptoms and so are often unaware of their status.

If both parents are carriers of the sickle trait, they have a 25 per cent chance of having a child with SCD for each pregnancy.

One in 10 persons in Jamaica is a carrier of the sickle gene and another one in 15 persons carries another gene which puts them at risk of having a child with SCD.