Sickle cell disease is a blood disorder in which the body produces an abnormal type of the oxygen-carrying substance hemoglobin in the red blood cells. Normal hemoglobin is called hemoglobin A, but people with sickle cell disease have only hemoglobin S, which turns normal, round red blood cells into abnormally curved (sickle) shapes.

Sickle-shaped blood cells are destroyed by the body faster than normal blood cells, which can result in an inadequate oxygen supply to the body (anemia). Most people with sickle cell disease have at least mild symptoms of chronic anemia, including:

• Weakness and fatigue.
• A pale appearance.
• Yellowing of the skin and the whites of the eyes (jaundice).
• Shortness of breath.

Sickle-shaped blood cells are also more likely to get stuck in and block small blood vessels throughout the body. Reduced blood flow caused by blocked blood vessels can damage certain organs, muscles, and bones. This may cause repeated episodes of pain (called sickle cell crises) that may last from hours to days. The pain most often occurs in the bones of the spine, arms and legs, the chest, and the abdomen.

People who have sickle cell disease need special medical care throughout their lives to treat the variety of problems that can be caused by the illness.