Sickle cell anaemia
What is it?
Sickle cell anemia is an inherited form of anaemia — a condition in which there aren't enough healthy red blood cells to carry adequate oxygen throughout your body.
Normally, your red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anemia, the red blood cells become rigid, sticky and are shaped like sickles or crescent moons. These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.
There's no cure for most people with sickle cell anemia. However, treatments can relieve pain and help prevent further problems associated with sickle cell anaemia.
Signs and symptoms of sickle cell anemia usually show up after an infant is 4 months old and may include:
- Anaemia. Sickle cells are fragile. They break apart easily and die, leaving you chronically short on red blood cells. Red blood cells usually live for about 120 days before they die and need to be replaced. However, sickle cells die after only 10 to 20 days. The result is a chronic shortage of red blood cells, known as anemia. Without enough red blood cells in circulation, your body can't get the oxygen it needs to feel energized. That's why anemia causes fatigue.
- Episodes of pain. Periodic episodes of pain, called crises, are a major symptom of sickle cell anemia. Pain develops when sickle-shaped red blood cells block blood flow through tiny blood vessels to your chest, abdomen and joints. Pain can also occur in your bones. The pain may vary in intensity and can last for a few hours to a few weeks. Some people experience only a few episodes of pain. Others experience a dozen or more crises a year. If a crisis is severe enough, you may need hospitalization so that pain medication can be injected into your veins (intravenously).
- Hand-foot syndrome. Swollen hands and feet may be the first signs of sickle cell anemia in babies. The swelling is caused by sickle-shaped red blood cells blocking blood flow out of their hands and feet.
- Jaundice. Jaundice is a yellowing of the skin and eyes that occurs because of liver damage or dysfunction. Occasionally, people who have sickle cell anemia have some degree of jaundice because the liver, which filters harmful substances from the blood, is overwhelmed by the rapid breakdown of red blood cells. In people with dark skin, jaundice is visible mostly as yellowing of the whites of the eyes.
- Frequent infections. Sickle cells can damage your spleen, an organ that fights infection. This may make you more vulnerable to infections. Doctors commonly give infants and children with sickle cell anemia antibiotics to prevent potentially life-threatening infections, such as pneumonia.
- Delayed growth. Red blood cells provide your body with the oxygen and nutrients you need for growth. A shortage of healthy red blood cells can slow growth in infants and children and delay puberty in teenagers.
- Vision problems. Some people with sickle cell anemia experience vision problems. Tiny blood vessels that supply your eyes may become plugged with sickle cells. This can damage the retina — the portion of the eye that processes visual images.
Sickle cell anemia is caused by a mutation in the gene that tells your body to make hemoglobin — the red, iron-rich compound that gives blood its red color. Haemoglobin is a component of every red blood cell. It allows red blood cells to carry oxygen from your lungs to all parts of your body, and to carry carbon dioxide waste from throughout your body to your lungs so that it can be exhaled.
Under normal circumstances, your body makes healthy hemoglobin known as haemoglobin A. People with sickle cell anemia make hemoglobin S — the S stands for sickle.
The sickle cell gene is passed from generation to generation in a pattern of inheritance called autosomal recessive inheritance. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected.
People with sickle cell trait have one normal haemoglobin gene and one defective form of the gene. So their bodies make both normal haemoglobin and sickle cell haemoglobin. Their blood may contain some sickle cells, but they generally don't experience symptoms. However, they are carriers of the disease, which means they can pass the defective gene on to their children.
With each pregnancy, two people with sickle cell traits have:
- A 25 percent chance of having an unaffected child with normal haemoglobin
- A 50 percent chance of having a child who also is a carrier
- A 25 percent chance of having a child with sickle cell anemia
The risk of inheriting sickle cell anemia comes down to genetics. For a baby to be born with sickle cell anaemia, both parents must carry a sickle cell gene.
The gene is particularly common among people with African, Spanish, Mediterranean, Middle Eastern and Indian ancestry.
Sickle cell anemia can lead to a host of complications, including:
- Stroke. A stroke can occur if sickle cells block blood flow to an area of your brain. Stroke is one of the most serious complications of sickle cell anemia. Signs of stroke include seizures, weakness or numbness of your arms and legs, sudden speech difficulties, and loss of consciousness. If your baby or child has any of these signs and symptoms, seek medical treatment immediately. A stroke can be fatal.
- Acute chest syndrome. This life-threatening complication of sickle cell anemia causes chest pain, fever and difficulty breathing. Acute chest syndrome can be caused by a lung infection or by sickle cells blocking blood vessels in your lungs. It requires emergency medical treatment with antibiotics, blood transfusions and drugs that open up airways in your lungs. Recurrent attacks can damage your lungs.
- Pulmonary hypertension. About one-third of people with sickle cell anemia will eventually develop high blood pressure in their lungs (pulmonary hypertension). Shortness of breath and difficulty breathing are common symptoms of this condition, which can ultimately lead to heart failure.
- Organ damage. Sickle cells can block blood flow through blood vessels, immediately depriving an organ of blood and oxygen. In sickle cell anemia, blood is also chronically low on oxygen. Chronic deprivation of oxygen-rich blood can damage nerves and organs in your body, including your kidneys, liver and spleen. Organ damage can be fatal.
- Blindness. Tiny blood vessels that supply your eyes can get blocked by sickle cells. Over time, this can damage the retina — the portion of the eye that processes visual images — and lead to blindness.
- Skin ulcers. Sickle cell anemia can cause open sores, called ulcers, on your legs.
- Gallstones. The breakdown of red blood cells produces a substance called bilirubin. Bilirubin is responsible for yellowing of the skin and eyes (jaundice) in people with sickle cell anemia. A high level of bilirubin in your body can also lead to gallstones.
- Priapism. Men with sickle cell anemia may experience painful erections, a condition called priapism. As occurs in other parts of the body, sickle cells can block the blood vessels in the penis. This can damage the penis and eventually lead to impotence.
A blood test can check for hemoglobin S — the defective form of hemoglobin that underlies sickle cell anemia. In the United States, this blood test is part of routine newborn screening done at the hospital. But older children and adults can be tested too.
In adults, a blood sample is drawn from a vein in the arm. In young children and babies, the blood sample is usually collected from a finger or heel. The sample is then sent to a laboratory, where it's screened for hemoglobin S.
If the screening test is negative, there is no sickle cell gene present. If the screening test is positive, further tests will be done to determine whether one or two sickle cell genes are present. People who have one gene — sickle cell trait — have a fairly small percentage of hemoglobin S. People with two genes — sickle cell disease — have a much larger percentage of the defective hemoglobin.
To confirm any diagnosis, a sample of blood is examined under a microscope to check for large numbers of sickle cells — a marker of the disease. If you or your child has the disease, a blood test to check for anemia — a low red blood cell count — will be done. And your doctor may suggest additional tests to check for possible complications of the disease.
If you or your child carries the sickle cell gene, you may be referred to a genetic counselor — an expert in genetic diseases.
Sickle cell anemia can be diagnosed in an unborn baby by sampling some of the fluid surrounding the baby in the mother's womb (amniotic fluid) to look for the sickle cell gene.
Once diagnosed with sickle cell anemia, your child will need to see his or her doctor more often than most children do. For children under 2, ask your child's doctor how frequently checkups need to be scheduled. For youngsters over age 2, at least two visits a year are usually scheduled.