Normal red blood cells are disc-shaped and look like doughnuts without holes in the center. They move easily through your blood vessels. Red blood cells contain an iron-rich protein called hemoglobin (HEE-muh-glow-bin). This protein carries oxygen from the lungs to the rest of the body.
Sickle cells contain abnormal hemoglobin called sickle hemoglobin or hemoglobin S. Sickle hemoglobin causes the cells to develop a sickle, or crescent, shape.
Sickle cells are stiff and sticky. They tend to block blood flow in the blood vessels of the limbs and organs. Blocked blood flow can cause pain, serious infections, and organ damage.
Sickle cell anemia is one type of anemia. Anemia is a condition in which your blood has a lower than normal number of red blood cells. This condition also can occur if your red blood cells don’t contain enough hemoglobin.
Red blood cells are made in the spongy marrow inside the large bones of the body. Bone marrow is always making new red blood cells to replace old ones. Normal red blood cells live about 120 days in the bloodstream and then die. They carry oxygen and remove carbon dioxide (a waste product) from your body.
In sickle cell anemia, the number of red blood cells is low because sickle cells don’t last very long. Sickle cells usually die after only about 10 to 20 days. The bone marrow can’t make new red blood cells fast enough to replace the dying ones.
Sickle cell anemia is an inherited, lifelong disease. People who have the disease are born with it. They inherit two genes for sickle hemoglobin—one from each parent.
People who inherit a sickle hemoglobin gene from one parent and a normal gene from the other parent have a condition called sickle cell trait.