Health Resources

What is sickle cell disease?
Sickle cell disease (SCD) is a group of inherited red blood cell disorders. If you have SCD, there is a problem with your hemoglobin. Hemoglobin is a protein in red blood cells that carries oxygen throughout the body. With SCD, the hemoglobin forms into stiff rods within the red blood cells. This changes the shape of the red blood cells. The cells are supposed to be disc-shaped, but this changes them into a crescent, or sickle, shape.

The sickle-shaped cells are not flexible and cannot change shape easily. Many of them burst apart as they move through your blood vessels. The sickle cells usually only last 10 to 20 days, instead of the normal 90 to 120 days. Your body may have trouble making enough new cells to replace the ones that you lost. Because of this, you may not have enough red blood cells. This is a condition called anemia, and it can make you feel tired.

The sickle-shaped cells can also stick to vessel walls, causing a blockage that slows or stops the flow of blood. When this happens, oxygen can't reach nearby tissues. The lack of oxygen can cause attacks of sudden, severe pain, called pain crises. These attacks can occur without warning. If you get one, you might need to go to the hospital for treatment.

What causes sickle cell disease?

Mutations in the HBB gene cause sickle cell disease.

Hemoglobin consists of four protein subunits, typically, two subunits called alpha-globin and two subunits called beta-globin. The HBB gene provides instructions for making beta-globin. Various versions of beta-globin result from different mutations in the HBB gene. One particular HBB gene mutation produces an abnormal version of beta-globin known as hemoglobin S (HbS). Other mutations in the HBB gene lead to additional abnormal versions of beta-globin such as hemoglobin C (HbC) and hemoglobin E (HbE). HBB gene mutations can also result in an unusually low level of beta-globin; this abnormality is called beta thalassemia.

In people with sickle cell disease, at least one of the beta-globin subunits in hemoglobin is replaced with hemoglobin S. In sickle cell anemia, which is a common form of sickle cell disease, hemoglobin S replaces both beta-globin subunits in hemoglobin. In other types of sickle cell disease, just one beta-globin subunit in hemoglobin is replaced with hemoglobin S. The other beta-globin subunit is replaced with a different abnormal variant, such as hemoglobin C. For example, people with sickle-hemoglobin C (HbSC) disease have hemoglobin molecules with hemoglobin S and hemoglobin C instead of beta-globin. If mutations that produce hemoglobin S and beta thalassemia occur together, individuals have hemoglobin S-beta thalassemia (HbSBetaThal) disease.

Abnormal versions of beta-globin can distort red blood cells into a sickle shape. The sickle-shaped red blood cells die prematurely, which can lead to anemia. Sometimes the inflexible, sickle-shaped cells get stuck in small blood vessels and can cause serious medical complications.

What are the symptoms of sickle cell disease?

People with SCD start to have signs of the disease during the first year of life, usually around 5 months of age. Early symptoms of SCD may include:

- Painful swelling of the hands and feet
- Fatigue or fussiness from anemia
- A yellowish color of the skin (jaundice) or the whites of the eyes (icterus)
The effects of SCD vary from person to person and can change over time. Most of the signs and symptoms of SCD are related to complications of the disease. They may include severe pain, anemia, organ damage, and infections.

How is sickle cell disease diagnosed?

A blood test can show if you have SCD or sickle cell trait. All states now test newborns as part of their screening programs, so treatment can begin early.

People who are thinking about having children can have the test to find out how likely it is that their children will have SCD.

Doctors can also diagnose SCD before a baby is born. That test uses a sample of amniotic fluid (the liquid in the sac surrounding the baby) or tissue taken from the placenta (the organ that brings oxygen and nutrients to the baby).

What are the treatments for sickle cell disease?

The only cure for SCD is bone marrow or stem cell transplantation. Because these transplants are risky and can have serious side effects, they are usually only used in children with severe SCD. For the transplant to work, the bone marrow must be a close match. Usually, the best donor is a brother or sister.

There are treatments that can help relieve symptoms, lessen complications, and prolong life:

- Antibiotics to try to prevent infections in younger children
- Pain relievers for acute or chronic pain
- Hydroxyurea, a medicine that has been shown to reduce or prevent several SCD complications. It increases the amount of fetal hemoglobin in the blood. This medicine is not right for everyone; talk to your health care provider about whether you should take it. This medicine is not safe during pregnancy.
- Childhood immunizations to prevent infections
- Blood transfusions for severe anemia. If you have had some serious complications, such as a stroke, you may have transfusions to prevent more complications.
There are other treatments for specific complications.

To stay as healthy as possible, make sure that you get regular medical care, live a healthy lifestyle, and avoid situations that may set off a pain crisis.