Sickle Cell Disease (SCD) is the term used to describe a group of inherited disorders characterised by the production of an abnormal 'sickle' haemoglobin. The sickle point mutation of the beta gene affects the quality of the beta chain produced. The most common abnormal sickle haemoglobin is sickle cell anaemia (Hb bSbS), commonly written (HbSS). In this instance an abnormal 'sickle' haemoglobin gene has been inherited from both parents. Other common types include sickle haemoglobin C disease (Hb bSbC) commonly written (Hb SC) and sickle beta thalassaemia (Hb bSbThal), commonly written as (HbSbThal). Less common types include sickle haemoglobin D disease (HbSD) and sickle haemoglobin E disease (HbSE).

In SCD there is a sickle-shaped abnormality of the red blood cells. The sickle haemoglobin acquires a crystal-like formation when exposed to low oxygen tension. The oxygen in veins is low enough to cause this change and consequently the cells containing sickle haemoglobin become deformed, rigid and sickle shaped in the venous circulation. These deformed sickle shaped cells become lodged in the small blood vessels and slow or obstruct the flow of blood to the surrounding tissues causing infarction (death of the tissue). The infarction causes painful crises, known as sickle cell or vaso-occlusive crises, the hallmark of sickle cell disease. In addition the sickled cells have only a short life span due to being constantly damaged when trying to flow through the blood vessels which results in a chronic haemolytic anaemia. There is also an increased susceptibility to infections. Sufferers can be mildly, moderately or severely affected, and their pattern of pain and other problems can vary over time.

When people have sickle trait condition, they have both HbA and HbS in their blood cells. People with sickle trait are well and do not have anaemia.

If you would like to know more about sickle cell disease visit the following websites:

•  Brent Sickle Cell and Thalassaemia Centre
•  Sickle Cell Society