Home   >   Medicine   >   Blood Disorders
Sickle Cell Anemia

Sickle cell anemia is a serious disease in which the body makes sickle-shaped red blood cells. “Sickle-shaped” means that the red blood cells are shaped like a "C."

In the United States, it’s estimated that sickle cell anemia affects 70,000–100,000 people, mainly African Americans. The disease occurs in about 1 out of every 500 African American births. Sickle cell anemia also affects Hispanic Americans. The disease occurs in 1 out of every 36,000 Hispanic American births.

Sickle Cells

Normal red blood cells are disc-shaped and look like doughnuts without holes in the center. They move easily through your blood vessels. Red blood cells contain the protein hemoglobin. This iron-rich protein gives blood its red color and carries oxygen from the lungs to the rest of the body.

Sickle cells contain abnormal hemoglobin that causes the cells to have a sickle shape. Sickle-shaped cells don’t move easily through your blood vessels. They’re stiff and sticky and tend to form clumps and get stuck in the blood vessels. (Other cells also may play a role in this clumping process.)

The clumps of sickle cells block blood flow in the blood vessels that lead to the limbs and organs. Blocked blood vessels can cause pain, serious infections, and organ damage.

Image

Figure A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. Figure B shows abnormal, sickled red blood cells clumping and blocking blood flow in a blood vessel. (Other cells also may play a role in this clumping process.) The inset image shows a cross-section of a sickle cell with abnormal hemoglobin.

Red blood cells are made in the spongy marrow inside the large bones of the body. Bone marrow is always making new red blood cells to replace old ones. Normal red blood cells last about 120 days in the bloodstream and then die. In sickle cell anemia, a lower-than-normal number of red blood cells occurs because sickle cells don’t last very long. Sickle cells usually die after only about 10 to 20 days. The bone marrow can’t make new red blood cells fast enough to replace the dying ones.

Causes

Sickle cell anemia is an inherited disease. People who have the disease inherit two copies of the sickle cell gene—one from each parent. The sickle cell gene causes the body to make abnormal hemoglobin. Hemoglobin is the iron-rich protein that gives blood its red color and carries oxygen from the lungs to the rest of the body.

Symptoms

The signs and symptoms of sickle cell anemia vary. Some people have mild symptoms. Others have very severe symptoms and often are hospitalized for treatment.

Sickle cell anemia is present at birth, but many infants don't show any signs until after 4 months of age.

The most common symptom of anemia is fatigue (feeling tired or weak). Other signs and symptoms of anemia include:

  • Shortness of breath
  • Dizziness
  • Headache
  • Coldness in the hands and feet
  • Pale skin
  • Chest pain

Sudden pain throughout the body is a common symptom of sickle cell anemia. This pain is called a "sickle cell crisis." Sickle cell crises often affect the bones, lungs, abdomen, and joints. A sickle cell crisis occurs when sickled red blood cells form clumps in the bloodstream. (Other cells also may play a role in this clumping process.) These clumps of cells block blood flow through the small blood vessels in the limbs and organs. This can cause pain and organ damage.

Diagnosis

Early diagnosis of sickle cell anemia is very important. Children who have the disease need prompt and proper treatment. In the United States, all States mandate testing for sickle cell anemia as part of their newborn screening program. The test uses blood from the same blood samples used for other routine newborn screening tests. It can show whether a newborn infant has sickle cell anemia or sickle cell trait.

Treatment

Sickle cell anemia has no widely available cure. However, treatments can help relieve symptoms and treat complications. The goals of treating sickle cell anemia are to relieve pain; prevent infections, eye damage, and strokes; and control complications (if they occur).

Treating Pain

Medicines and Fluids

Mild pain often is treated with over-the-counter medicine and heating pads. Severe pain may need to be treated in a hospital.

The usual treatments for acute (short-term) pain crises are fluids and pain-killing medicines. Fluids help prevent dehydration, a condition in which your body doesn't have enough fluids. Fluids are given either by mouth or through a vein.

Common medicines used to treat pain crises include acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), and narcotics such as meperidine, morphine, oxycodone, and others. (Narcotic abuse and addiction are issues that must be considered in any pain control plan.)

Treatment for mild-to-moderate pain usually begins with NSAIDs or acetaminophen. If pain continues, a narcotic may be added. Moderate-to-severe pain is often treated with narcotics. The narcotic may be used alone or with NSAIDs or acetaminophen.

Hydroxyurea

If you have severe sickle cell anemia, you may need a medicine called hydroxyurea. This medicine helps reduce the number of painful crises you have. Hydroxyurea is used to prevent painful crises, not to treat them when they occur.

Given daily, this medicine reduces how often painful crises and acute chest syndrome occur. People taking the medicine also need fewer blood transfusions and have fewer hospital visits.

Early studies of hydroxyurea in children show that they have improved growth. These studies also suggest that this medicine may help preserve organ function.

Hydroxyurea can cause serious side effects, including an increased risk for dangerous infections. People who take hydroxyurea must be carefully watched. Your doctor may need to adjust the dose of this medicine to reduce the risk for side effects.

Doctors are studying the long-term effects of hydroxyurea on people who have sickle cell anemia. Studies are under way to find out whether hydroxurea prevents organ damage or other sickle cell complications.

Preventing Complications

Blood transfusions are commonly used to treat worsening anemia and sickle cell complications. A sudden worsening of anemia due to an infection or enlargement of the spleen is a common reason for a blood transfusion.

Some, but not all, people who have sickle cell anemia need blood transfusions to prevent life-threatening problems such as stroke or pneumonia.

Having routine blood transfusions can cause side effects. Patients must be carefully watched. Side effects can include a dangerous buildup of iron in the blood (which must be treated) and an increased risk of infection from the transfused blood.

Infections

Infections are a major complication of sickle cell anemia. In fact, pneumonia is the leading cause of death in children who have sickle cell anemia. Other common infections linked to sickle cell anemia include meningitis, influenza, and hepatitis.

If a child who has sickle cell anemia shows early signs of an infection, such as fever, seek treatment right away.

To prevent infections in babies and young children, treatments include:

  • Daily doses of penicillin. Treatment may begin as early as 2 months of age and continue until the child is at least 5 years old.
  • All routine vaccinations (such as a yearly flu shot) plus the meningococcal vaccine.

Adults who have sickle cell anemia also should have flu shots every year and get vaccinated for pneumonia.

Eye Damage

Sickle cell anemia can damage the blood vessels in the eyes. Parents should ask their child's doctor about regular checkups with an eye doctor who specializes in diseases of the retina. The retina is a thin layer of tissue inside the back of the eye.

Adults who have sickle cell anemia also should have regular checkups with an eye doctor.

Strokes

Stroke prevention and treatment is now possible for children and adults who have sickle cell anemia. Starting at age 2, children who have sickle cell anemia often get routine ultrasound scans of their heads. This is called transcranial Doppler ultrasound. These scans are used to check blood flow in the brain.

The scans allow doctors to find out which children are at high risk for a stroke. These children are then treated with routine blood transfusions. This treatment has been found to greatly reduce the number of strokes in children.

New Treatments

Research on bone marrow transplants, gene therapy, and new medicines for sickle cell anemia is ongoing. The hope is that these studies will provide better treatments for sickle cell anemia. Researchers also are looking for a way to predict the severity of the disease.

Bone Marrow Transplant

A bone marrow transplant can work well for treating sickle cell anemia. This treatment may even offer a cure in a small number of cases. However, the procedure is risky and can lead to serious side effects or even death. Because of this, only some people can or should have this procedure. Bone marrow transplants usually are used only for young patients who have severe sickle cell anemia. However, the decision to give this treatment is made on a case-by-case basis.

Bone marrow used for a transplant must come from a closely matched donor. This is usually a close family member who doesn't have sickle cell anemia.

Gene Therapy

Gene therapy is being studied as a possible treatment for sickle cell anemia. Researchers want to know whether a normal gene can be put in the bone marrow of a person who has sickle cell anemia. This would cause the body to make normal red blood cells. Researchers also are studying whether they can "turn off" the sickle cell gene or "turn on" a gene that makes red blood cells behave normally.

New Medicines

Researchers are studying several new medicines for sickle cell anemia. These include:

  • Butyric acid. This is a food additive that may increase normal hemoglobin in the blood.
  • Nitric oxide. This medicine may make sickle cells less sticky and keep blood vessels open. People who have sickle cell anemia have low levels of nitric oxide in their blood.
  • Decitadine. This medicine increases hemoglobin F levels (this type of hemoglobin carries more oxygen). It may be a good choice instead of hydroxyurea.

 

Source

National Heart, Lung, and Blood Institute, USA.