Sickle Cell Disease
What is sickle cell disease?
Sickle cell disease is a disorder that affects the red blood cells, which use a protein called hemoglobin to transport oxygen from the lungs to the rest of the body. Normally, red blood cells are round and flexible so they can travel freely through the narrow blood vessels.
The hemoglobin molecule has two parts: an alpha and a beta. Patients with sickle cell disease have a mutation in a gene on chromosome 11 that codes for the beta subunit of the hemoglobin protein. As a result, hemoglobin molecules don't form properly, causing red blood cells to be rigid and have a concave shape (like a sickle used to cut wheat). These irregularly shaped cells get stuck in the blood vessels and are unable to transport oxygen effectively, causing pain and damage to the organs.
How do people get sickle cell disease?
Sickle cell disease is inherited in an autosomal recessive pattern. This means that a child will not inherit the disease unless both parents pass down a defective copy of the gene. People who inherit one good copy of the gene and one mutated copy are carriers. They are clinically normal, but can still pass the defective gene to their children.
What are the symptoms of sickle cell disease?
Sickle cell disease prevents oxygen from reaching the spleen, liver, kidneys, lungs, heart, or other organs, causing a lot of damage. Without oxygen, the cells that make up these organs will begin to die. For example, the spleen is often destroyed in these patients resulting in some loss of immune function. As a result, these patients often experience frequent infections.
The red blood cells of patients with sickle cell disease don't live as long as healthy red blood cells. As a result, people with this disorder often have low red blood cell counts (anemia), which is why this disease is commonly referred to as sickle cell anemia.
When sickle-shaped red blood cells get stuck in blood vessels this can cause episodes of pain called crises. Other symptoms include: delayed growth, strokes, and jaundice (yellowish hue to the skin and eyes because of liver damage).
Because of these complications, people with this disorder are likely to have their life span reduced by about 30 years.
How do doctors diagnose sickle cell disease?
Most states routinely screen newborns for sickle cell disease with a simple blood test.
If the disorder is not detected at birth, a blood sample can be used in a test called hemoglobin electrophoresis. This test will determine whether a person has sickle cell disease, or whether he or she is a carrier of the faulty hemoglobin gene.
How is sickle cell disease treated?
Babies and young children with sickle cell disease must take a daily dose of penicillin to prevent potentially deadly infections. Patients also take folic acid, which helps build new red blood cells.
Doctors advise people with sickle cell disease to get plenty of rest, drink lots of water, and avoid too much physical activity.
Blood transfusions that provide a patient with healthy red blood cells are a common treatment.
People with more severe cases of the disease can be treated with a bone marrow transplant. This procedure provides the patient with healthy red blood cells from a donor, ideally from a sibling.
Interesting facts about sickle cell disease
Unlike normal red blood cells, which can live for 120 days, sickle-shaped cells live only 10 to 20 days.
In the United States, the disease most commonly affects African-Americans. About 1 out of every 500 African-American babies born in the United States has sickle cell anemia.
Sickle cell disease is most common among people from Africa, India, the Caribbean, the Middle East, and the Mediterranean. The high prevalence of the defective gene in these regions may be due to the fact that carriers of a mutation in the beta-subunit of hemoglobin are more resistant to malaria. Malaria is a disease caused by a parasite that is transmitted to a person when they are bitten by an infected mosquito. The sometimes fatal disease is common in hot countries, and causes recurring chills and fever.