SCDA What is Sickle Cell?

What is Sickle Cell?

Sickle Cell Disease (SCD) is an inherited blood disorder that affects red blood cells. People with SCD have red blood cells that contain mostly hemoglobin S (S stands for Sickle), an abnormal type of hemoglobin. Sometimes these red blood cells become sickle-shaped (crescent-shaped) and have difficulty passing through small blood vessels.

When sickle-shaped cells block small blood vessels, less blood can reach that part of the body. Tissue that does not receive a normal blood flow eventually becomes damaged. This is what causes the complications of SCD. There is currently no universal cure for SCD.

SCD causes chronic anemia leading to fatigue and less endurance. Another common side effect of the clogging is pain, which can occur anywhere in the body. Patients with SCD are more likely to develop infections which can become life-threatening. SCD can also cause strokes because sickled-cells cause the clogging of blood vessels in the head.

Hemoglobin is the main substance of the red blood cell. It helps red blood cells carry oxygen from the air in our lungs to all parts of the body. Normal red blood cells contain hemoglobin A. Hemoglobin S and hemoglobin C are abnormal types of hemoglobin. Normal red blood cells are soft and round and can squeeze through tiny blood tubes (vessels). Normally, red blood cells live for about 120 days before new ones replace them.

People with sickle cell conditions make a different form of hemoglobin A called hemoglobin S. Red blood cells containing mostly hemoglobin S do not live as long as normal red blood cells (normally about 16 days). They also become stiff, distorted in shape and have difficulty passing through the body's small blood vessels. When sickle-shaped cells block small blood vessels, less blood can reach that part of the body. Tissue that does not receive a normal blood flow eventually becomes damaged. This is what causes the complications of SCD.

Types of SCD

There are several types of SCD. The most common are: Sickle Cell Anemia; Sickle-Hemoglobin C Disease; Sickle Beta-Plus Thalassemia; and Sickle Beta-Zero Thalassemia.

What is Sickle Cell Trait?

Sickle Cell trait is an inherited condition in which both hemoglobin A and S are produced in the red blood cells, always more A than S. Sickle cell trait is not a type of SCD. People with sickle cell trait are generally healthy.

Inheritance

Sickle cell conditions are inherited from parents in much the same way as blood type, hair color and texture, eye color and other physical traits. The types of hemoglobin a person makes in the red blood cells depend upon what hemoglobin genes the person inherits from his or her parents. Like most genes, hemoglobin genes are inherited in two sets - one from each parent.

Examples:

If one parent has Sickle Cell Anemia and the other is Normal, all of the children will have sickle cell trait.

If one parent has Sickle Cell Anemia and the other has Sickle Cell Trait, there is a 50 percent chance of having a baby with either SCD or sickle cell trait with each pregnancy.

When both parents have Sickle Cell Trait, they have a 25 percent chance of having a baby with SCD with each pregnancy.

How will I know if I have the Trait?

A simple, painless blood test, followed by a laboratory technique called Hemoglobin Electrophoresis will determine the type of hemoglobin you have. When you pass an electric charge through a solution of hemoglobin, distinct hemoglobins move different distances, depending on their composition. This technique differentiates between normal hemoglobin A, Sickle hemoglobin S, and other kinds of hemoglobin (such as C, D, E, etc.).

Medical Problems

Sickle cells are destroyed rapidly in the body of people with the disease causing anemia, jaundice and the formation of gallstones.

The sickle cells also block the flow of blood through vessels resulting in lung tissue damage (acute chest syndrome), pain episodes (arms, legs, chest and abdomen), stroke and priapism (painful prolonged erection). It also causes damage to most organs including the spleen, kidneys and liver. Damage to the spleen makes SCD patients, especially young children, easily overwhelmed by certain bacterial infections.

Treatment

Health maintenance for patients with SCD starts with early diagnosis, preferably in the newborn period and includes penicillin prophylaxis, vaccination against pneumococcus bacteria and folic acid supplementation.

Treatment of complications often includes antibiotics, pain management, intravenous fluids, blood transfusion and surgery — all backed by psycho-social support. Like all patients with chronic disease, patients are best managed in a comprehensive multi-disciplinary program of care.

Blood transfusions help benefit SCD patients by reducing recurrent pain crises, risk of stroke and other complications. Because red blood cells contain iron, and there is no natural way for the body to eliminate it, patients who receive repeated blood transfusions can accumulate iron in the body until it reaches toxic levels. It is important to remove excess iron from the body because it can gather in the heart, liver, or other organs and may lead to organ damage. Treatments are available to eliminate iron overload.

Promising Treatment Developments

In search for a substance that can prevent red blood cells from sickling without causing harm to other parts of the body, Hydroxyurea was found to reduce the frequency of severe pain, acute chest syndrome and the need for blood transfusions in adult patients with SCD. Droxia, the prescription form of hydroxyurea, was approved by the FDA in 1998 and is now available for adult patients with sickle cell anemia. Further research is being conducted to determine proper treatment for children.

Other treatment options in clinical development include new, more convenient options than current therapies to eliminate iron overload caused by repeated blood transfusions.