Sickle-cell disease (SCD) is an inherited form of anemia where the red blood cells change from the normal round (similar to a doughnut) shape to a long pointed shape like a sickle or banana. These sickled red blood cells have difficulty flowing through the blood vessels and can get stuck. The body recognizes these red blood cells as abnormal and destroys them faster than usual resulting in anemia.
How Does Someone Get SCD?
Sickle-cell disease is inherited, therefore a person is born with it. For a person to inherit SCD, both parents must have either sickle cell trait or sickle cell disease. In rarer forms of SCD, one parent has sickle trait and the other parent has hemoglobin C trait or beta thalassemia trait. When both parents have sickle trait (or another trait), they have a 1 in 4 chance of having a child with SCD. This risk occurs every pregnancy.
Types of Sickle-Cell Disease
The most common form of sickle-cell disease is called hemoglobin SS. The other major types are: hemoglobin SC, sickle beta zero thalassemia, and sickle beta plus thalassemia. Hemoglobin SS and sickle beta zero thalassemia are the most severe forms of sickle-cell disease and are sometimes referred to as sickle cell anemia. Hemoglobin SC disease is considered moderate and in general, sickle beta plus thalassemia is the mildest form of sickle-cell disease.
How Are People Diagnosed With Sickle-Cell Disease?
In the United States, all newborns are tested for SCD shortly after birth as part of the newborn screening program. If the results are positive for SCD, the child’s pediatrician or a local sickle cell center is informed of the results so the patient can be seen in a sickle cell clinic. In countries that do not perform newborn screening testing, people are often diagnosed with SCD as children when they start to experience symptoms.
Symptoms of SCD
Because SCD is a disorder of the red blood cells the entire body can be affected.
- Pain: When the sickled red blood cells get trapped in a blood vessel, blood cannot flow to an area of the bone. This results in a lack of oxygen to this area and pain.
- Infections: Because the spleen (an organ in the immune system) does not function properly, people with sickle-cell disease are at higher risk for severe bacterial infections. This is why young children with sickle-cell disease take penicillin twice daily.
- Stroke: If the sickled red blood cells get trapped in a blood vessel in the brain, a portion of the brain doesn’t get oxygen which results in a stroke. This may present as a facial droop, weakness of the arms or legs, or difficulty with speech. Strokes can happen in children with sickle-cell disease and similar to adults with stroke, this is a medical emergency.
- Fatigue (or tiredness): Because people with sickle-cell disease are anemic, they may experience decreased energy or fatigue.
- Gallstones: When the red blood cells break down (called hemolysis) in sickle-cell disease, they release bilirubin. This buildup of bilirubin can then lead to the development of gallstones.
- Priapism: If sickle cells become trapped in the penis, this results in a painful, unwanted erection known as priapism.
Treatment of SCD
- Penicillin: Twice a day, penicillin is started shortly after diagnosis (usually before 2 months of age). Taking penicillin twice daily until the age of 5 has been proven to decrease the risk of serious bacterial infections.
- Immunizations: Immunizations can also reduce the risk of serious bacterial infections.
- Blood transfusions: Blood transfusions can be used to treat specific complications of sickle-cell disease like severe anemia or acute chest syndrome, a lung complication. Also, patients with sickle-cell disease who have had a stroke or are at high risk for a stroke receive blood transfusions on a monthly schedule to prevent further problems.
- Hydroxyurea: Hydroxyurea is the only FDA approved medication to treat sickle-cell disease. Hydroxyurea has been proven to reduce anemia and complications of sickle-cell disease like pain and acute chest syndrome.
- Bone marrow transplantation: Bone marrow transplantation is the only cure for sickle-cell disease. The best success for this treatment comes when a matched sibling is able to donate stem cells.