SICKLE CELL DISEASE

This section is dedicated to sickle cell disorders.

THE MAJOR SICKLE CELL DISORDERS ARE:

Sickle cell anaemia, sickle cell disease (HbS/HbS)
HbS/β-thalassaemia
HbSC disease
HbSD disease
HbS/EHbS/O Arab

Many diseases in humans are caused by abnormalities in the blood and these are categorized according to the component of the blood which is affected: white cell diseases, platelet diseases and red cell diseases.

Haemoglobin disorders or haemoglobinopathies are a group of conditions affecting human blood – more specifically an important substance or protein called haemoglobin contained in the red blood cells, hence the name haemoglobin disorders or haemoglobinopathies.

Haemoglobin is a protein that consists of the alpha (α) and beta (β) parts or chains and which are in turn produced by the α-globin genes and β-globin genes respectively. Hence the diseases caused by haemoglobin abnormality either with regards to its production or its structure are divided into α-chain diseases (or α-globin gene) diseases and β-chain (β-globin gene) diseases. These genes are found on chromosomes 16 and 11 respectively.

Amongst the β-chain diseases, a number of abnormal haemoglobins are included, such as HbC, HbD, HbPunjab, HbE, HbO Arab and sickle cell disorders (SCD). The latter are related to the most severe clinical outcome and the haemoglobin responsible for the development of these disorders is known as Haemoglobin S (HbS) – the letter Sderiving from the word sickle which describes the shape red cells assume when they contain this haemoglobin in their contents.

In the case of abnormal haemoglobins, the structure and not the production of normal, adult haemoglobin is affected and as such it is the quality and not the quantity of haemoglobin that is affected.