Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Sickle Cell Anemia

What Is It?

Sickle cell anemia is an inherited blood disorder.

It causes:

• Chronic destruction of red blood cells

• Episodes of intense pain

• Vulnerability to infections

• Organ damage

• In some cases, early death

Hemoglobin is a protein in red blood cells that carries oxygen. People with sickle cell anemia have a type of hemoglobin that forms long rods. The long rods stretch the red blood cells into long, abnormal "sickle" shapes. In contrast, normal red blood cells are disc-shaped.

Sickle-shaped red blood cells cannot easily pass through the body's blood vessels. Instead, they clog blood vessels. They block the flow of blood and cut off the oxygen supply to tissues and organs.

This lack of oxygen can damage the body's organs and limbs. It causes severe pain in any affected area.

Sickled blood cells last only 10 to 20 days in the bloodstream. A normal red cell's lifespan is 120 days. So, sickling causes chronic anemia--an abnormally low level of red blood cells.

The spleen is an organ that helps clear infections. Sickle cell disease damages the spleen. By the time a child with sickle cell anemia is 4 years old, the spleen has usually stopped functioning. As a result, people with sickle cell disease have an increased risk of developing life-threatening infections.

To have fully developed sickle cell anemia, you must inherit one gene for the illness from each parent. Sometimes a person inherits only one sickle cell gene from one parent. This person is said to have sickle cell "trait" rather than sickle cell anemia. People with sickle cell trait usually have no symptoms. But, they can pass the gene to their children.