Sickle Cell Disease (SCD)

Sickle cell disease (SCD) is a disease of hemoglobin, a molecule that carries oxygen within red blood cells. In SCD, defective hemoglobin causes the red blood cells to become stiff instead of flexible and form a sickle or a crescent. SCD is an inherited disease, meaning that the disease is passed on from parents to children through genes. Genes are instructions that tell the body how to make all the different substances the body needs to work properly. Since SCD is inherited, the disease is present at birth. In SCD, a child inherits two defective hemoglobin genes (called hemoglobin S), one from each parent. This causes the body to make faulty hemoglobin. If a child inherits just one defective hemoglobin S gene, and the other hemoglobin gene is normal (hemoglobin A), he or she will have sickle cell trait, and will not have any SCD symptoms.   Abstract source