Sickle cell anemia is an inherited condition in which the red blood cells become abnormally shaped. It may lead to pain or a number of other serious complications, including stroke, life-threatening infection or end-organ damage. The disease is present at birth, and symptoms typically begin early in childhood.

Red blood cells transport vital oxygen to the limbs and organs. These cells are normally disc-shaped. In people with sickle cell anemia, a large number of these red blood cells become sickle- or crescent-shaped. This sickle-shape is caused by the presence of an abnormal hemoglobin called hemoglobin S. Hemoglobin, a protein molecule present in all red blood cells, is responsible for transporting oxygen from the lungs to the tissues around the body. Normally red blood cells contain hemoglobin A. With hemoglobin S, the amount of oxygen transported in the red blood cells is reduced.

As a result of the reduced oxygen, the cells change shape. These sickle-shaped cells are harmful because they often get stuck in small blood vessels, obstructing the flow of blood. This can lead to a number of complications, including recurrent episodes of pain known as sickle cell crises, although this term is falling out of favor among the medical establishment.

These structurally abnormal cells also become very fragile and are broken down prematurely, at a rate faster than the body can replace them. While a normal red blood cell typically lives for about 90 days, a sickle cell typically lasts only 16 days. As a result, patients with sickle cell anemia often have a lower-than-normal number of red blood cells in their blood, a condition called anemia. This can lead to a number of symptoms, including fatigue, jaundice (yellowing of skin and eyes), shortness of breath, and delayed growth and development in children.

Sickle cell anemia can only affect someone who has inherited hemoglobin S from both parents. A person who inherits hemoglobin S from only one parent can have sickle cell trait. Known as carriers, these people with sickle cell trait usually have no symptoms. They can, however, pass the trait on to their children.

To determine if a person has sickle cell anemia or sickle cell trait, physicians may order a number of blood tests (e.g., hemoglobin electrophoresis, sickle cell test). Newborns are routinely screened for the abnormal gene in many states. Adults, older children and fetuses can also be screened.

According to the Sickle Cell Disease Association of America, there are approximately 70,000 people living with sickle cell anemia in the United States. Most of these patients are African-American and Hispanic.

Currently, bone marrow transplant is the only cure for sickle cell anemia. However, the procedure is risky, and it is often difficult to find a suitable bone marrow donor. When a bone marrow transplant is not an option, the focus of treatment is on relieving pain and preventing crises (recurrent episodes of pain) and other complications.

Common treatment methods include medication, especially with hydroxyurea, (to control pain and reduce the number of crises), vaccinations and blood transfusions. A number of additional treatment methods are also being studied that may cause the body to produce more hemoglobin, such as the use of hydroxyurea.  

In the past, people with sickle cell anemia often died between the ages of 20 and 40, usually because of organ failure. However, medical advancements have enabled most people with sickle cell anemia to live well into their 40s and 50s.

Couples in which both partners carry the sickle cell gene may be able to lower the risk of having a child with sickle cell anemia with an in vitro fertilization technique known as preimplantation genetic diagnosis. This procedure allows physicians to implant eggs that are free of the defective gene into a woman for development.