Sickle cell anemia
Medically reviewed on Mar 8, 2018
Sickle cell anemia is an inherited form of anemia — 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 and 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. But treatments can relieve pain and help prevent problems associated with the disease.
Normal red blood cells are round. In sickle cell anemia, some red blood cells become deformed, so they look like sickles used to cut wheat. These unusually shaped cells give the disease its name.
Signs and symptoms of sickle cell anemia, which vary from person to person and change over time, include:
Anemia. Sickle cells break apart easily and die, leaving you without enough red blood cells. Red blood cells usually live for about 120 days before they need to be replaced. But sickle cells usually die in 10 to 20 days, leaving a shortage of red blood cells (anemia).
Without enough red blood cells, your body can't get the oxygen it needs to feel energized, causing 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 varies in intensity and can last for a few hours to a few weeks. Some people have only a few pain episodes. Others have a dozen or more crises a year. If a crisis is severe enough, you might need to be hospitalized.
Some adolescents and adults with sickle cell anemia also have chronic pain, which can result from bone and joint damage, ulcers and other causes.
- Painful swelling of hands and feet. The swelling is caused by sickle-shaped red blood cells blocking blood flow to the hands and feet.
- Frequent infections. Sickle cells can damage an organ that fights infection (spleen), leaving you more vulnerable to infections. Doctors commonly give infants and children with sickle cell anemia vaccinations and 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. 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, leading to vision problems.
When to see a doctor
Although sickle cell anemia is usually diagnosed in infancy, if you or your child develops any of the following problems, see your doctor right away or seek emergency medical care:
- Unexplained episodes of severe pain, such as pain in the abdomen, chest, bones or joints.
- Swelling in the hands or feet.
- Abdominal swelling, especially if the area is tender to the touch.
- Fever. People with sickle cell anemia have an increased risk of infection, and fever can be the first sign of an infection.
- Pale skin or nail beds.
- Yellow tint to the skin or whites of the eyes.
- Signs or symptoms of stroke. If you notice one-sided paralysis or weakness in the face, arms or legs; confusion; trouble walking or talking; sudden vision problems or unexplained numbness; or a headache, call 911 or your local emergency number right away.
Sickle cell anemia is caused by a mutation in the gene that tells your body to make the red, iron-rich compound that gives blood its red color (hemoglobin). Hemoglobin allows red blood cells to carry oxygen from your lungs to all parts of your body. In sickle cell anemia, the abnormal hemoglobin causes red blood cells to become rigid, sticky and misshapen.
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.
If only one parent passes the sickle cell gene to the child, that child will have the sickle cell trait. With one normal hemoglobin gene and one defective form of the gene, people with the sickle cell trait make both normal hemoglobin and sickle cell hemoglobin. Their blood might contain some sickle cells, but they generally don't have symptoms. But they are carriers of the disease, which means they can pass the gene to their children.
For a baby to be born with sickle cell anemia, both parents must carry a sickle cell gene. In the United States, it most commonly affects black people.
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. 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 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 might require emergency medical treatment with antibiotics and other treatments.
- Pulmonary hypertension. People with sickle cell anemia can develop high blood pressure in their lungs (pulmonary hypertension). This complication usually affects adults rather than children. Shortness of breath and fatigue are common symptoms of this condition, which can be fatal.
- Organ damage. Sickle cells that block blood flow through blood vessels immediately deprive the affected 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. Sickle cells can block tiny blood vessels that supply your eyes. Over time, this can damage the portion of the eye that processes visual images (retina) and lead to blindness.
- Leg 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. A high level of bilirubin in your body can lead to gallstones.
- Priapism. Men with sickle cell anemia can have painful, long-lasting 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 lead to impotence.
If you carry the sickle cell trait, seeing a genetic counselor before trying to conceive can help you understand your risk of having a child with sickle cell anemia. He or she can also explain possible treatments, preventive measures and reproductive options.
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.
If you or your child has sickle cell anemia, a blood test to check for a low red blood cell count (anemia) will be done. Your doctor might suggest additional tests to check for possible complications of the disease.
If you or your child carries the sickle cell gene, you'll likely be referred to a genetic counselor.
Tests to detect sickle cell genes before birth
Sickle cell disease 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. If you or your partner has been diagnosed with sickle cell anemia or sickle cell trait, ask your doctor about whether you should consider this screening. Ask for a referral to a genetic counselor who can help you understand the risk to your baby.
Bone marrow transplant, also known as stem cell transplant, offers the only potential cure for sickle cell anemia. It's usually reserved for people younger than age 16 because the risks increase for people older than 16. Finding a donor is difficult, and the procedure has serious risks associated with it, including death.
As a result, treatment for sickle cell anemia is usually aimed at avoiding crises, relieving symptoms and preventing complications. Babies and children age 2 and younger with sickle cell anemia should make frequent visits to a doctor. Children older than 2 and adults with sickle cell anemia should see a doctor at least once a year, according to the Centers for Disease Control and Prevention.
Treatments might include medications to reduce pain and prevent complications, and blood transfusions, as well as a bone marrow transplant.
Medications used to treat sickle cell anemia include:
Antibiotics. Children with sickle cell anemia may begin taking the antibiotic penicillin when they're about 2 months old and continue taking it until they're at least 5 years old. Doing so helps prevent infections, such as pneumonia, which can be life-threatening to an infant or child with sickle cell anemia.
As an adult, if you've had your spleen removed or had pneumonia, you might need to take penicillin throughout your life.
- Pain-relieving medications. To relieve pain during a sickle cell crisis, your doctor might prescribe pain medications.
Hydroxyurea (Droxia, Hydrea). When taken daily, hydroxyurea reduces the frequency of painful crises and might reduce the need for blood transfusions and hospitalizations. Hydroxyurea seems to work by stimulating production of fetal hemoglobin — a type of hemoglobin found in newborns that helps prevent the formation of sickle cells.
Hydroxyurea increases your risk of infections, and there is some concern that long-term use of this drug might cause problems later in life for people who take it for many years. More study is needed.
Your doctor can help you determine if this drug might be beneficial for you or your child. Don't take the drug if you're pregnant.
Assessing stroke risk
Using a special ultrasound machine (transcranial), doctors can learn which children have a higher risk of stroke. This painless test, which uses sound waves to measure blood flow, can be used on children as young as 2 years. Regular blood transfusions can decrease stroke risk.
Vaccinations to prevent infections
Childhood vaccinations are important for preventing disease in all children. They're even more important for children with sickle cell anemia because their infections can be severe.
Your doctor will make sure your child receives all of the recommended childhood vaccinations. Vaccinations, such as the pneumococcal vaccine and the annual flu shot, are also important for adults with sickle cell anemia.
In a red blood cell transfusion, red blood cells are removed from a supply of donated blood, then given intravenously to a person with sickle cell anemia.
Blood transfusions increase the number of normal red blood cells in circulation, helping to relieve anemia. In children with sickle cell anemia at high risk of stroke, regular blood transfusions can decrease the risk. Transfusions can also be used to treat other complications of sickle cell anemia, or they can be given to prevent complications.
Blood transfusions carry some risk, including infection and excess iron buildup in your body. Because excess iron can damage your heart, liver and other organs, people who undergo regular transfusions might need treatment to reduce iron levels.
Bone marrow transplant
A bone marrow transplant, also called a stem cell transplant, involves replacing bone marrow affected by sickle cell anemia with healthy bone marrow from a donor. The procedure usually uses a matched donor, such as a sibling, who doesn't have sickle cell anemia. For many, donors aren't available. But stem cells from umbilical cord blood might be an option.
Because of the risks associated with a bone marrow transplant, the procedure is recommended only for people, usually children, who have significant symptoms and problems from sickle cell anemia.
If a donor is found, the person with sickle cell anemia receives radiation or chemotherapy to destroy or reduce his or her bone marrow stem cells. Healthy stem cells from the donor are injected intravenously into the bloodstream of the person with sickle cell anemia, where they migrate to the bone marrow and begin generating new blood cells.
The procedure requires a lengthy hospital stay. After the transplant, you'll receive drugs to help prevent rejection of the donated stem cells. Even so, your body might reject the transplant, leading to life-threatening complications.
Treating sickle cell complications
Doctors treat most complications of sickle cell anemia as they occur. Treatment might include antibiotics, vitamins, blood transfusions, pain-relieving medicines, other medications and possibly surgery, such as to correct vision problems or to remove a damaged spleen.
Scientists are studying new treatments for sickle cell anemia, including:
Gene therapy. Researchers are exploring whether inserting a normal gene into the bone marrow of people with sickle cell anemia will result in normal hemoglobin. Scientists are also exploring the possibility of turning off the defective gene while reactivating another gene responsible for the production of fetal hemoglobin — a type of hemoglobin found in newborns that prevents sickle cells from forming.
Potential treatments using gene therapy are a long way off, however.
- Nitric oxide. People with sickle cell anemia have low levels of nitric oxide in their blood. Nitric oxide is a gas that helps keep blood vessels open and reduces the stickiness of red blood cells. Treatment with inhaled nitric oxide might prevent sickle cells from clumping together. Studies on nitric oxide have shown little benefit so far.
- Drugs to boost fetal hemoglobin production. Researchers are studying various drugs to devise a way to boost the production of fetal hemoglobin. This is a type of hemoglobin that stops sickle cells from forming.
Lifestyle and home remedies
Taking the following steps to stay healthy may help you avoid complications of sickle cell anemia:
- Take folic acid supplements daily, and choose a healthy diet. Bone marrow needs folic acid and other vitamins to make new red blood cells. Your doctor might recommend a folic acid supplement. Choose a diet that focuses on a variety of colorful fruits and vegetables, as well as whole grains.
- Drink plenty of water. Dehydration can increase your risk of a sickle cell crisis. Drink water throughout your day, aiming for about eight glasses a day. Increase the amount of water you drink if you exercise or spend time in a hot, dry climate.
- Avoid temperature extremes. Exposure to extreme heat or cold can increase your risk of a sickle cell crisis.
- Exercise regularly, but don't overdo it. Talk with your doctor about how much exercise is right for you.
- Use over-the-counter (OTC) medications with caution. Use OTC pain medications, such as ibuprofen (Advil, Motrin IB, Children's Motrin, others) or naproxen sodium (Aleve) sparingly, if at all, because of the possible effect on your kidneys. Ask your doctor before taking OTC drugs.
Coping and support
If you or someone in your family has sickle cell anemia, you may want help with the stresses of this lifelong disease. Consider:
- Finding someone to talk with. Sickle cell centers and clinics can provide information and counseling. Ask your doctor or the staff at a sickle cell center if there are support groups for families in your area. Talking with others who are facing the same challenges you are can be helpful.
- Exploring ways to cope with the pain. Work with your doctor to find ways to control your pain. Pain medications can't always take all the pain away. Different techniques work for different people, but it might be worth trying heating pads, hot baths, massages or physical therapy.
- Learning about sickle cell anemia to make informed decisions about care. If you have a child with sickle cell anemia, learn as much as you can about the disease. Ask questions during your child's appointments. Ask your health care team to recommend good sources of information.
Preparing for an appointment
Sickle cell anemia is usually diagnosed through genetic screening done when a baby is born. Those test results will likely be given to your family doctor or pediatrician. He or she will likely refer you to a doctor who specializes in blood disorders (hematologist) or a pediatric hematologist.
Here's information to help you get ready for your appointment.
What you can do
Make a list of:
- Symptoms you've noticed, including any that seem unrelated to the reason for which you scheduled the appointment
- Key personal information, including family medical history and whether anyone has sickle cell anemia or has a trait for it
- Questions to ask your doctor
Bring a family member or friend along, if possible, to help you remember the information you're given.
For sickle cell anemia, questions to ask your doctor include:
- What's the most likely cause of my child's symptoms?
- Are there other possible causes?
- What tests are needed?
- What treatments are available and which do you recommend?
- What side effects are common with these treatments?
- Are there alternatives to the primary approach that you're suggesting?
- What's my child's prognosis?
- Are there dietary or activity restrictions?
- Do you have brochures or other printed material that I can have? What websites do you recommend?
Don't hesitate to ask other questions.
What to expect from your doctor
Your doctor is likely to ask you questions, including:
- When did you notice your child's symptoms?
- Have they been continuous or occasional?
- What, if anything, seems to improve symptoms?
- What, if anything, seems to worsen them?