Sickle cell anemia is a genetic blood disorder in which the body produces sickle- or crescent-shaped red blood cells. This abnormal shape makes it difficult for blood to flow through blood vessels and impairs the cells' ability to efficiently carry oxygen to the body's tissues and organs. Affected cells often stick to blood vessel walls, increasing the risk for blocked arteries to the brain that can cause stroke. Blockages in the coronary arteries of the heart can lead to heart attack. This disorder mainly affects African-Americans.