Haemoglobin is the substance in red blood cells that is responsible for the colour of the cell and for carrying oxygen around the body.
People with sickle cell disorder are born with the condition, it is not contagious. It can only be inherited from both parents each having passed on the gene for sickle cell.
The main symptoms of sickle cell disorder are anaemia and episodes of severe pain. The pain occurs when the cells change shape after oxygen has been released. The red blood cells then stick together, causing blockages in the small blood vessels.
These painful episodes are referred to as sickle cell crisis. They are treated with strong painkillers such as morphine to control the pain.
People with sickle cell are at risk of complications stroke, acute chest syndrome, blindness, bone damage and priapism (a persistent, painful erection of the penis).
Over time people with sickle cell can experience damage to organs such as the liver, kidney, lungs, heart and spleen. Death can also result from complications of the disorder. Treatment of sickle cell mostly focuses on preventing and treating complications.
The only possible cure for the disorder is bone marrow transplant but this is only possible for a limited number of affected individuals who have a suitable donor. A medicine called Hydroxyurea, can significantly reduce the number of painful crises.