What is Sickle Cell Disorder?

Sickle Cell Disorder is an inherited disease in which the red blood cells, normally disc-shaped, become crescent shaped. As a result, they function abnormally and break down, causing recurrent painful episodes.

Causes and risks

Sickle cell anemia results from a condition in which a person's red blood cells carry almost exclusively an abnormal type of hemoglobin, called Hemoglobin S. For this to occur, the person must have received a Hemoglobin S gene from each parent.

If a person has received a Hemoglobin S gene from only one parent, and a normal hemoglobin gene from the other, that person is said to have sickle trait. Persons with sickle trait rarely have problems and, unless tested, may be unaware that they carry the gene. A few people with sickle trait have problems at high altitudes, where there is less oxygen.  The chances of inheriting sickle cell anemia from parents with the sickle cell trait is illustrated below.

Someone who inherits hemoglobin S from one parent and another type of abnormal hemoglobin from the other parent will have another form of sickle cell disease such as sickle cell-b 0 thalassemia, hemoglobin SC disease, or sickle cell-b + thalassemia. Persons with these forms of sickle cell anemia rarely have problems and, unless tested, may be unaware that they carry the gene.  The inheritance of sickle trait is illustrated below.

Sickle cell anemia may become life threatening when damaged red blood cell break down (hemolytic crisis) or bone marrow fails to produce blood cells (aplastic crises). Repeated crises can cause damage to the kidneys, lungs, bone, liver (incidence less than two percent), and Blocked blood vessels and damaged organs can cause painful episodes.

These painful crises, which occur in 70% of patients, can last hours to days, affecting the bones of the back, the long bones and the chest. Some patients have one episode every few years, while others have many episodes per year. The crises can be severe enough to require admission to the hospital for pain control and intravenous fluids.

Many manifestations of this disease are a result of the fragility and inflexibility of the sickle red blood cells. When patients experience, infection, and low oxygen supply, these fragile red blood cells assume a crescent shape, causing red blood cell destruction and thickening of the blood.

Prevention

Sickle cell anemia can only result when two carriers with sickle cell trait have a child together. Therefore, genetic counseling is recommended for all carriers of sickle cell trait. Prenatal diagnosis of sickle cell anemia is also available. Prompt treatment of infections, adequate oxygenation, and preventing dehydration may prevent sickling of red blood cells. Antibiotics and vaccinations may prevent infections. General health visits with a physician are recommended to ensure the patients are getting adequate nutrition, maintaining proper activity levels, and receiving proper vaccinations.

In incentive spirometry, the patient breathes into a plastic tube that has a ball inside. By trying to breathe hard enough to force the ball up the tube, the patient receives more oxygen. Using this treatment when chest pains begin may decrease the complications of acute chest syndrome. Prenatal diagnosis is now possible for couples at risk of producing a child with sickle cell anemia.

Treatment

Researchers have found that several chemical compounds, including urea, carbamyl phosphate, and sodium cyanate, can reverse the sickling process. However, these drugs can have serious side effects and, under some testing procedures, have not proved as effective as researchers originally hoped. Researchers are experimenting with these and other drugs in an effort to find a safe, effective treatment. Currently, blood transfusions are usually given only when the anemia is severe enough to cause serious illness.