What causes sickle cell anaemia?
Sickle cell anaemia is caused by a defect in the gene that is the “blueprint” for haemoglobin: the defective gene gives instructions for making sickle haemoglobin. Children who inherit a copy of the defective gene from each of his/her parents develop sickle cell anaemia. Children who inherit a copy from only one parent do not develop the disease, but have sickle cell trait, in other words, they will be carriers of the HbS gene. People with sickle cell trait usually have no symptoms, but can pass the HbS gene on to their children. They have enough normal haemoglobin to keep the red blood cells flexible, but need special care if they go under general anaesthetic, and are advised against activities involving below-normal oxygen levels, such as scuba diving or high altitude mountain-climbing. If both parents are carriers, with each conception there is a 25% chance the child will have sickle cell anaemia; a 25% chance of not having or carrying the disease; and a 50% chance of being a carrie
