Sickle cell anemia is one of a group of inherited disorders known as sickle cell disease. It affects the shape of red blood cells, which carry oxygen to all parts of the body.

Red blood cells are usually round and flexible, so they move easily through blood vessels. In sickle cell anemia, some red blood cells are shaped like sickles or crescent moons. These sickle cells also become rigid and sticky, which can slow or block blood flow.

The current approach to treatment is to relieve pain and help prevent complications of the disease. However, newer treatments may cure people of the disease.

Red blood cells and sickle cells

Sickle cell anemia

Red blood cells are usually round and flexible. In sickle cell anemia, some red blood cells look like sickles used to cut wheat. These unusually shaped cells give the disease its name.


Symptoms of sickle cell anemia usually appear around 6 months of age. They vary from person to person and may change over time. Symptoms can include:

  • Anemia. Sickle cells break apart easily and die. Typical 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. This is known as anemia. Without enough red blood cells, the body can't get enough oxygen. This causes fatigue.
  • Episodes of pain. Periodic episodes of extreme pain, called pain 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 the chest, abdomen and joints.

    The pain varies in intensity and can last for a few hours to a few days. Some people have only a few pain crises a year. Others have a dozen or more a year. A severe pain crisis requires a hospital stay.

    Some people with sickle cell anemia also have chronic pain from bone and joint damage, ulcers, and other causes.

  • Swelling of hands and feet. Sickle-shaped red blood cells block blood circulation in the hands and feet, which can cause them to swell.
  • Frequent infections. The spleen is important for protecting against infections. Sickle cells can damage the spleen, raising the risk of developing infections. Babies and children with sickle cell anemia commonly receive vaccinations and antibiotics to prevent potentially life-threatening infections, such as pneumonia.
  • Delayed growth or puberty. Red blood cells provide the body with the oxygen and nutrients needed for growth. A shortage of healthy red blood cells can slow growth in babies and children and delay puberty in teenagers.
  • Vision problems. Tiny blood vessels that supply blood to the eyes can become plugged with sickle cells. This can damage the portion of the eye that processes visual images, called the retina, and lead to vision problems.

When to see a doctor

See your healthcare professional right away if you or your child has symptoms of sickle cell anemia, including fever or stroke.

Infections often start with a fever and can be life-threatening. Because children with sickle cell anemia are prone to infections, seek prompt medical attention for a fever greater than 101.5 degrees Fahrenheit (38.5 degrees Celsius).

Seek emergency care for symptoms of stroke, which include:

  • One-sided paralysis or weakness in the face, arms or legs.
  • Confusion.
  • Difficulty walking or talking.
  • Sudden vision changes.
  • Unexplained numbness.
  • Severe headache.


Sickle cell anemia is caused by a change in the gene that tells the body to make hemoglobin. Hemoglobin is the iron-rich compound in red blood cells that allows these cells to carry oxygen from the lungs to the rest of the body. The hemoglobin associated with sickle cell anemia causes red blood cells to become rigid, sticky and misshapen.

For a child to have sickle cell anemia, both parents must carry one copy of the sickle cell gene and pass both copies to the child.

If only one parent passes the sickle cell gene to the child, that child will have the sickle cell trait. With one typical hemoglobin gene and one sickle cell gene, people with the sickle cell trait make both typical hemoglobin and sickle cell hemoglobin.

Their blood might contain some sickle cells, but they generally don't have symptoms. They're carriers of the disease. That means they can pass the gene to their children.

Risk factors

For a baby to have sickle cell anemia, both parents must carry a sickle cell gene. In the United States, sickle cell anemia most commonly affects people of African, Mediterranean and Middle Eastern descent.


Sickle cell anemia can lead to a host of complications, including:

  • Stroke. Sickle cells can block blood flow to the brain. Signs of stroke include seizures, weakness or numbness of the arms and legs, sudden speech difficulties, and loss of consciousness. If your child has any of these signs or symptoms, seek medical treatment right away. A stroke can be fatal.
  • Acute chest syndrome. A lung infection or sickle cells blocking blood vessels in the lungs can cause this life-threatening complication. Symptoms include chest pain, fever and difficulty breathing. Acute chest syndrome might need emergency medical treatment.
  • Avascular necrosis. Sickle cells can block the blood vessels that supply blood to the bones. When the bones don't get enough blood, joints may narrow and bones can die. This can happen anywhere but most often happens in the hip.
  • Pulmonary hypertension. People with sickle cell anemia can develop high blood pressure in their lungs. This complication usually affects adults. Shortness of breath and fatigue are common symptoms of this condition, which can be fatal.
  • Organ damage. Sickle cells that block blood flow to organs deprive the affected organs of blood and oxygen. In sickle cell anemia, blood also is low in oxygen. This lack of oxygen-rich blood can damage nerves and organs, including the kidneys, liver and spleen, and can be fatal.
  • Splenic sequestration. Sickle cells can get trapped in the spleen, causing it to enlarge. This may cause abdominal pain on the left side of the body and can be life-threatening. Parents of children with sickle cell anemia can learn how to locate and feel their child's spleen for enlargement.
  • Blindness. Sickle cells can block tiny blood vessels that supply blood to the eyes. Over time, this can lead to blindness.
  • Leg ulcers. Sickle cell anemia can cause painful open sores on the legs.
  • Gallstones. The breakdown of red blood cells produces a substance called bilirubin. A high level of bilirubin in the body can lead to gallstones.
  • Priapism. Sickle cell anemia can cause painful, long-lasting erections, known as priapism. Sickle cells can block the blood vessels in the penis, which can lead to impotence over time.
  • Deep vein thrombosis. Sickled red blood cells can cause blood clots, increasing the risk of a clot lodging in a deep vein, known as deep vein thrombosis. It also increases the risk of a blood clot lodging in a lung, known as pulmonary embolism. Either can cause serious illness or even death.
  • Pregnancy complications. Sickle cell anemia can increase the risk of high blood pressure and blood clots during pregnancy. It also can increase the risk of miscarriage, premature birth and low birth weight babies.


If you carry the sickle cell trait, it can help to see a genetic counselor before you get pregnant. A counselor can help you understand your risk of having a child with sickle cell anemia. You also can learn about possible treatments, preventive measures and reproductive options.

Dec 22, 2023

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