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Definition: sickle-cell anemia from Dictionary of DNA and Genome Technology

An inherited disorder involving the β-chain of hemoglobin; the mis-shaped erythrocytes (red blood cells) are eliminated, leading to (sometimes fatal) anemia.

Sickle-cell trait refers to the generally less serious condition in those heterozygous for the gene; it may be asymptomatic, and it confers a degree of resistance to falciparum malaria.

[Correction of the sickle-cell mutation in embryonic stem cells: Proc Natl Acad Sci USA (2006) 103(4):1036–1040.]

(See also THALASSEMIA.)


Summary Article: Sickle Cell Anemia
from Harvard Medical School Health Topics A-Z
What Is It?

Sickle cell anemia is an inherited blood disorder.

It causes:

  • Chronic destruction of red blood cells, causing severe anemia

  • Episodes of intense pain

  • Vulnerability to infections

  • Organ damage

  • In some cases, early death

Hemoglobin is a protein in red blood cells that carries oxygen. People with sickle cell anemia inherit a defective type of hemoglobin. When oxygen levels inside a red blood cell get low, the defective hemoglobin forms long rods. These rods stretch the red blood cells into long, abnormal "sickle" shapes. In contrast, normal red blood cells are disc-shaped.

Sickle-shaped red blood cells cannot easily pass through the body's blood vessels. Instead, they clog blood vessels. They block the flow of blood and cut off the oxygen supply to tissues and organs.

This lack of oxygen can damage the body's organs and limbs. It causes severe pain in any affected area.

A normal red cell's lifespan is 120 days. In contrast, sickled blood cells last only 10 to 20 days. As a result, patients with sickle cell disease have chronic anemia--an abnormally low level of red blood cells.

The spleen is an organ that helps clear infections. Sickle cell disease damages the spleen. By the time a child with sickle cell anemia is 4 years old, the spleen has usually stopped functioning. As a result, people with sickle cell disease have an increased risk of developing life-threatening infections.

To have fully developed sickle cell anemia, you must inherit one gene for the illness from each parent. Sometimes a person inherits only one sickle cell gene from one parent. This person is said to have sickle cell "trait" rather than sickle cell anemia. People with sickle cell trait usually have no symptoms. But, they can pass the gene to their children.

Symptoms

Symptoms of sickle cell anemia include:

  • Fatigue, shortness of breath, pale skin and fingernails due to anemia

  • Recurrent bouts of pain in the abdomen, chest, back, arms or legs

  • A yellowing of the skin and whites of the eyes

  • Slowed growth and delayed puberty in children

  • Frequent infections

  • Eye problems, including blindness

  • Stroke

When sickled red cells block blood vessels, the oxygen supply to body cells is obstructed. This causes painful episodes called crises. Painful sickle cell crises can affect many different joints and organs. The back, chest, extremities and abdomen are affected most commonly. The level of pain varies, from trivial to excruciating. The episodes typically last from two to seven days.

In about half the cases, the pain crisis is accompanied by:

  • Fever

  • Nausea

  • Vomiting

  • High blood pressure

  • Fast heart rate

These painful episodes can be triggered by many things. Triggers include:

  • Infection

  • Stress

  • Alcohol consumption

  • Dehydration

Women are more likely to experience a painful episode during their menstrual period.

But the majority of sickle cell crises have no identifiable cause.

Diagnosis

Your doctor will ask you about:

  • A history of painful crises

  • Neurological problems

  • Chest pain

  • History of infections

He or she then will perform a physical examination. It will focus on your heart, lungs, joints, eyes and neurological system.

Blood tests will be done. A complete blood count (CBC) can detect anemia. A microscopic examination of the blood may reveal the characteristic sickled cells. A blood test called hemoglobin electrophoresis confirms the diagnosis, by identifying the abnormal form of hemoglobin that is produced in people with the disease.

In families with a history of sickle cell anemia, a doctor may screen for the disorder whenever a new baby is born in your family. Prenatal screening also can be done.

Expected Duration

Sickle cell anemia is a lifelong condition.

Prevention

There is no way to prevent sickle cell anemia.

If sickle cell anemia or sickle cell trait runs in your family, you and your spouse may wish to speak with a genetic counselor. He or she can explain your chances of passing the condition to your children.

Treatment

Treatment of sickle cell anemia may include any of the following:

  • Folic acid supplements. To ensure that enough of this nutrient is available to make new red blood cells.

  • Vaccinations. To prevent the infections that are more likely to occur in people with sickle cell anemia, a person should be vaccinated for:

    • Pneumococcal pneumonia

    • Haemophilus influenza

    • Meningitis

    • Hepatitis A and B

    • Varicella

    • Rotavirus

    • Tetanus

    • Diphtheria

    • Pertussis

    • Influenza

    • Poliovirus (in those parts of the world where the virus persists)

  • Daily antibiotic therapy. To protect against infection in young children.

  • Fluids, oxygen and pain-killing medications. To manage episodes of painful crises.

  • Blood transfusions. To treat anemia and painful crises.

  • Hydroxyurea (Hydrea). This medication is used in adults. It seems to reduce the need for blood transfusions. It also decreases the frequency of acute chest syndrome and painful crises.

  • Routine eye exams. To detect early abnormalities. These can be treated with laser coagulation and other types of eye surgery to prevent vision loss.

For some children, a hematopoietic stem cell (bone marrow) transplant may cure their illness. The child has to have a sibling who is a suitable donor. However, this is a high-risk treatment. It is primarily used in those with very severe symptoms.

When To Call A Professional

People with sickle cell disease must see their doctor regularly and receive comprehensive care.

Call the doctor immediately when anyone with sickle cell disease:

  • Develops a fever or any other sign of infection

  • Has severe pain in any part of their body

  • Develops breathing problems

  • Develops any neurological symptoms

Prognosis

Sickle cell anemia affects different people differently. It follows no set pattern.

For example, some patients have only mild symptoms with less than one crisis episode per year. Others have more severe symptoms. Or they may average more than one crisis per month.

There is currently no cure for sickle cell anemia. But life expectancy for those with the illness has dramatically increased over the past 30 years.

Additional Info

National Heart, Lung, and Blood Institute (NHLBI)

P.O. Box 30105

Bethesda, MD 20824-0105

Phone: (301) 592-8573

TTY: (240) 629-3255

Fax: (301) 592-8563

http://www.nhlbi.nih.gov/

March of Dimes Birth Defects Foundation

1275 Mamaroneck Ave.

White Plains, NY 10605

Toll-Free: (888) 663-4637

http://www.modimes.org/

Sickle Cell Disease Association Of America

200 Corporate Pointe

Suite 495

Culver City, CA 90230-8727

Phone: (310) 216-6363

Fax: (310) 215-3722

Toll-Free: (800) 421-8453

http://www.sicklecelldisease.org/

Rapoza, Kristen
Copyright 2016 Harvard Health Publications

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