More About Sickle Cell Disease

Sickle Cell Disease (SCD) is an inherited disorder of the red blood cells (RBC's). The genes received from one's parents before birth determine whether a person will have SCD. SCD is not contagious.

Sickle Cell Disease happens at conception, when a person acquires his/her genes from their parents. With a few exceptions, a child can inherit sickle cell disease only if both parents have one sickle cell hemoglobin gene. If only one of the genes is a "sickle" gene and the other is normal, the person is a carrier for SCD. This condition is called sickle cell trait. With a few rare exceptions, people with sickle cell trait are usually completely normal. If both genes are "sickle" genes, then the person has Sickle Cell Disease. Also, sickle cell trait does not develop into sickle cell disease.

In most states, newborns are specially tested for Sickle Cell Disease. Routine "blood counts" commonly performed in doctors' offices do not diagnose the sickle cell trait.

SCD is caused by a small change in a hemoglobin protein contained in RBC's. In SCD, the red blood cells contain sickle hemoglobin, which causes them to change to a curved (sickle) shape after oxygen is released. Sickle-shaped cells become stuck and block the blood flow 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 most common types of SCD are:

Sickle cell anemia
Hemoglobin SC disease
Sickle beta-thalassemia

In the United States, most people who have SCD are African Americans. Among African-American children, about 1 every 375 has SCD. Hispanic Americans from the Caribbean, Central America, and parts of South America may also have the disease. SCD is also found in individuals from Turkey, Greece, Italy, the Middle East, and East India.

Treating Sickle Cell Disease

It is very important for babies and children with Sickle Cell Disease to receive the regular childhood vaccinations. One of these vaccinations, the Hib (Hemophilus influenzae b) vaccine, helps protect against a potentially life-threatening bacterial infection. It also is important that children with SCD receive the pneumococcal and meningococcal vaccines at ages 2 and 5 years or older. In addition to this, they should also have yearly flu (influenza) shots, beginning after 1 year of age.

An episode of pain that is caused by the sickle-shaped cells blocking blood flow is called a "pain crisis", and can be very severe. Until recently, there was no effective treatment to prevent the sickling that causes a pain crisis. Although treatment with a drug called hydroxyurea has been shown to reduce the number of pain crises in severely affected patients over 18 years of age who have had at least three painful crises in the previous year, this drug is not yet recommended for affected children.

While regular transfusions appear to benefit some people with SCD, this treatment has some risks that doctors and families must carefully weigh. For example: regular blood transfusions cause excessive amounts of iron to build up in the body. Because too much iron can damage the heart and other vital organs, people who undergo regular transfusions usually have to also have treatments to reduce iron levels. Regular transfusions also become less effective over time, and the period between transfusions must be decreased to maintain their effectiveness.

Some children with sickle cell disease have been cured through a bone marrow transplant (BMT), using donated bone marrow from an HLA matched sibling. Standard BMTs have some very serious risks, which prevent them from being used widely. We believe the Institute's approach to BMT makes it much safer by treating the donor bone marrow to remove harmful cells. This will make it possible to safely treat patients with sickle cell disease.
More about the Institute's Clinical Trial for Sickle Cell Disease

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