ABOUT SICKLE CELL DISEASE

ABOUT SICKLE CELL DISEASE: Sickle cell disease is a hereditary blood disorder that affects the red blood cells. People with this disease have red blood cells that mostly contain an abnormal type of hemoglobin. Hemoglobin is the main substance of the red blood cells, helping them carry oxygen from the air in our lungs to the different parts of the body. Normal red blood cells are smooth and round, like doughnuts, so they can squeeze through the blood vessels; they also live for about 120 days before new cells replace them. People with sickle cell disease have misshapen red blood cells, usually hard and pointed, and shaped like a sickle (crescent).

This makes it more likely for them to get stuck in small blood vessels and block the flow of blood, so that tissue throughout the body becomes oxygen deprived and damaged. These abnormal red blood cells also don't live as long as normal ones -- only about 16 days -- and the body simply can't make enough new red blood cells to keep up. With fewer red blood cells in the body, people with the disease can suffer from anemia, gallstones and jaundice, among other complications.

INHERITING SICKLE CELL DISEASE: Having sickle cell disease is not the same thing as carrying the sickle cell trait. People with sickle cell trait are generally healthy; they don't have the disease, but merely carry the gene that causes the disease. They can pass this gene on to their children. All sickle cell conditions are inherited from parents, just like blood type, and hair and eye color. If one of the parents has sickle cell anemia and the other is not a carrier of the trait, all of the children will have the sickle cell trait. In this case, there is a 50 percent chance of their child having the condition. If both parents have sickle cell trait, they have a 25 percent chance of having a baby with sickle cell anemia.

BACKGROUND

The first report of sickle cell disease was in a dental student from Grenada, Walter Clement Noel, who was studying in Chicago between 1904 and 1907. Dr. James Herrick and Dr. Ernest Irons were the first to identify the irreversibly sickled cells associated with his disease, described in their report as "very irregular, many elongated forms." Noel later returned to Grenada to set up a dental practice and died at age 32 of acute chest syndrome. Neel and Beet described homozygous inheritance in 1947–1949. The demonstration of abnormal electrophoretic mobility of the hemoglobin S beta chain in subjects with sickle cell disease and trait led to the proposal by Pauling that this was a molecular disease of hemoglobin (1949), followed by the observation that valine had replaced glutamic acid on the beta globin chain (Ingram and Hunt, 1956–1958