Sickle Cell Anemia

(Sickle Cell Disease)

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Definition | Causes | Risk Factors | Symptoms | Diagnosis | Treatment | Prevention | Organizations

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Definition

Sickle cell anemia is a group of genetic disorders that changes the composition of red blood cells. The genetic defect affects hemoglobin, which carries oxygen throughout the body.

Causes

Red blood cells are normally soft and round and move easily through the blood vessels. People with sickle cell anemia have an abnormal type of hemoglobin (hemoglobin S), which causes the red blood cells to become hard and sickle-shaped. Because of their odd shape, some of the "sickled" cells get stuck in the small blood vessels. There they break apart, causing blockages in the vessels. If the blockage occurs in a blood vessel that leads to a major organ, the decreased blood flow can cause severe pain and organ damage.

The body recognizes that sickled cells are abnormal, and destroys them faster than they can be replaced. This causes anemia, or a shortage of red blood cells, especially under the following conditions:

• Fever
• Infection
• Dehydration
• Drop in oxygen or change in air pressure (sometimes occurs during airplane travel)

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

• Genetics: Children who inherit copies of the defective gene from both parents will have sickle cell anemia. Children who inherit only one copy of the gene will not have sickle cell disease, but will carry the trait.
• Race: Blacks of sub-Saharan origin
• Ethnicity: Greeks, Italians, and people from some parts of India and the Arabian Peninsula

Symptoms

Sickle cell anemia produces a group of symptoms known as a sickle cell crisis. These are episodes of pain that occur with varying frequency and severity, and are usually followed by periods of remission. The risk for a sickle cell crisis increases with any activity that boosts the body's requirement for oxygen, such as illness, physical stress, or high altitudes.

These painful crises can last hours to days. They affect the bones of the back, the long bones, and the chest. The crises can be severe enough to require hospital admission for pain control and intravenous fluids.

Symptoms of impending sickle cell crisis include:

• Pain and swelling in the hands and feet
• Fever
• Jaundice
• Anemia
• Chest pain, or episodic pain in joints, abdomen, or back
• Shortness of breath
• Fatigue
• Abdominal swelling
• Unusual or prolonged headache
• Any sudden weakness or loss of sensation
• Priapism (prolonged erection)
• Sudden vision changes
• Sudden, severe anemia can cause:
  • Weakness
  • Shortness of breath
  • Heart failure
  • Shock
  • Loss of consciousness

Complications of sickle cell anemia include:

• Destruction of the spleen
• Severe bacterial infections:
  • Pneumonia
  • Meningitis
  • Kidney and bone infections
• Damage to the joints (especially hip and shoulder)
• Gallstones
• Damage to eyes, resulting in impaired vision
• Stroke
• Seizures
• Liver disease
• High rate of Hepatitis C
• Damage to penis, due to priapism (may result in impotence)
• Leg ulcers
• Heart murmurs or enlarged heart
• Delayed growth
• Delayed sexual development

Diagnosis

Hemoglobin electrophoresis is a simple blood test that can be done by a doctor or local sickle cell foundation. Most states require testing of newborns for sickle cell disease or sickle cell trait. Amniocentesis (a form of prenatal testing) can also detect sickle cell disease.

Treatment

Basic treatment of sickle cell crises includes:

• Bedrest
• Pain relief medications
• Oral and intravenous fluids
• Oxygen - to reduce pain and prevent complications.

In addition, treatment may include:

Penicillin

The National Institutes of Health recommends that newborns with sickle cell disease take penicillin twice a day, beginning at age 2 months and continuing until least 5 years of age.

Pneumococcal Vaccine

The American Academy of Pediatrics recommends that children with sickle cell disease who are 2-5 years of age receive pneumococcal vaccine (PCV-7).

Hydroxyurea

Hydroxyurea (Hydrea) is a drug used to treat certain types of leukemia and other cancers. It is the first drug to significantly prevent complications of sickle cell disease. Hydroxyurea increases the production of fetal hemoglobin, which decreases the number of deformed red blood cells. Therefore, it reduces the frequency of sickle cell crises.

Hydrea is not appropriate for everyone with sickle cell disease. The U.S. Food and Drug Administration (FDA) recommends that hydroxyurea be given only to patients over age 18 who have had at least three painful crises in the previous year.

Blood Transfusions

Blood transfusions can treat and prevent some of the complications of sickle cell anemia. Regular transfusion therapy can help prevent recurring strokes in children.

Bone Marrow Transplant

A bone marrow transplant from a matched donor who doesn't have the sickle cell gene may be effective. There are medical risks involved, however, and recipients must take drugs that suppress the immune system for the rest of their lives.

Prevention

Sickle cell anemia cannot be prevented because it is a genetic defect. However, there are some general guidelines that may keep the condition under control. Be sure to discuss these with your health care provider.

• Daily folic acid supplements, to build new red blood cells
• Drink plenty of water, to prevent dehydration.
• Avoid temperature extremes.
• Avoid overexertion and stress.
• Get plenty of rest.
• Get regular check-ups with knowledgeable health care providers.
• Genetic counseling.

Organizations

The Sickle Cell Information Center
http://www.emory.edu/PEDS/SICKLE/sicklept.htm

American Sickle Cell Anemia Association
http://www.ascaa.org/

SOURCES:

National Institutes of Health

"Sickle cell anemia and antisickling agents then and now." Current Medical Chemistry, February 2001.

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Last reviewed June 2001 by Medical Review Board