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Skip Navigation U.S. Department of Health and Human Services
Agency for Healthcare Research Quality
Understanding Your Body

What Is Sickle Cell Disease?

Sickle cell disease is an inherited disorder of the red blood cells. Red blood cells carry oxygen to all parts of the body by using a protein called hemoglobin. Normal red blood cells contain only normal hemoglobin and are shaped like doughnuts. These cells are very flexible and move easily through small blood vessels.

But in sickle cell disease, the red blood cells contain sickle hemoglobin, which causes them to change to a curved shape (sickle shape) after oxygen is released. Sickled cells become stuck and form plugs in small blood vessels. This blockage of blood flow can damage the tissue. Because there are blood vessels in all parts of the body, damage can occur anywhere in the body.

The image at the top shows a normal red blood cell (which appears oval in shape) while the image at the bottom shows a Sickled cell, which has lost its original oval shape and adopted a more flat, spiny-pointed shape. The most common types of sickle cell disease are:
  • Sickle cell anemia.
  • Hemoglobin SC disease.
  • Sickle beta-thalassemia.

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