Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link
Quick Facts

Sickle Cell Disease


The Manual's Editorial Staff

Last full review/revision Jan 2021| Content last modified Jan 2021
Click here for the Professional Version
Get the full details
Topic Resources

What is sickle cell disease?

Sickle cell disease is a lifelong problem with your red blood cells. It's something you’re born with that causes some of your red blood cells to be unusually shaped. Instead of being shaped like disks, they're shaped like sickles (crescents).

The sickle shape of the red blood cells is because they contain an abnormal form of hemoglobin. Hemoglobin is the substance in red blood cells that carries oxygen. The sickle shape causes the red blood cells to break easily and not fit through small blood vessels to deliver oxygen.

  • Sickle cell disease is most common in blacks who come from Africa

  • Sickle cell disease makes your red blood cells break apart easily, causing low blood count (anemia)

  • The abnormal blood cells can't pass easily through your smallest blood vessels, causing pain, poor growth, and eventually problems with organs such as your kidneys and spleen

  • People with sickle cell disease are more likely to get certain infections

  • Doctors diagnose sickle cell disease with a blood test

  • Treatment is aimed at relieving symptoms, but stem cell therapy may offer a cure for some people

What causes sickle cell disease?

Sickle cell disease is caused by genes your parents pass down to you. It runs in families. You need two sickle cell genes, one from each parent, to have sickle cell disease.

What is sickle cell trait?

Sickle cell trait is when you have only one copy of the sickle cell gene. If the other copy of the gene is normal, then you don't have sickle cell disease.

If two people with sickle cell trait have children, half of their children will have the trait, one quarter will have sickle cell disease, and one quarter will be normal. People with sickle cell disease (not just the trait) are often unable to have children.

What are the complications of sickle cell disease?

Not all red blood cells have the sickle shape when you have sickle cell disease. The more sickle-shaped cells you have, the more likely you are to have symptoms and complications. Low oxygen levels and other factors make your red blood cells more likely to become sickle shaped.

The abnormal red blood cells break down easily. The breakdown can cause:

  • Low blood count (anemia)

  • Yellow color of the eyes and sometimes skin (jaundice)

The abnormal red blood cells don't pass through tiny blood vessels easily, so organs don't get enough blood. When blood flow is blocked, your symptoms depend on what body parts are affected:

  • Bones: Pain (painful crisis), damage to the hip joints

  • Brain: Stroke

  • Heart: Enlarged heart, heart failure

  • Kidneys: Kidney failure, kidney pain

  • Lungs: Acute chest syndrome

  • Penis: Priapism (prolonged, painful erection)

  • Skin: Chronic skin sores

  • Spleen: Shrunken spleen, which increases the risk of certain infections

Aplastic crisis is when your bone marrow suddenly stops making new red blood cells and your anemia gets worse very quickly.

What are the symptoms of sickle cell disease?

People who have sickle cell disease all have:

  • Symptoms of anemia (feeling weak and tired and looking pale)

Some people have few other symptoms, while others have severe symptoms with enormous disability and early death.

Sickle cell crisis

A sickle cell painful crisis is when some parts of your body aren't getting enough oxygen. Signs and symptoms of a painful crisis include:

  • Pain in your belly, back, or the long bones of your arms and legs

  • Fever

  • Throwing up

A sickle cell crisis can be caused by anything that lowers the oxygen level in your blood:

  • Strong exercise

  • Mountain climbing

  • Flying at high altitudes without enough oxygen

  • An illness

Acute chest syndrome is another problem that can occur during a sickle cell crisis. Acute chest syndrome usually occurs in children and can be deadly. Symptoms include:

  • Severe chest pain

  • Problems breathing from low oxygen levels in the blood

How can doctors tell if I have sickle cell disease?

Doctors will tell you have sickle cell disease from:

  • Blood tests

You may need further testing, depending on your symptoms.

What are screening tests for sickle cell disease?

Screening tests are tests doctors do on people who don't have symptoms. Doctors often do screening blood tests for sickle cell disease on:

  • Parents, brothers, and sisters of people with sickle cell disease

  • Newborn babies soon after birth

Doctors can also test you and your partner before you have a baby to see if you carry the sickle cell trait and may pass it on (carrier screening).

How do doctors treat sickle cell disease?

Doctors treat sickle cell disease to:

  • Prevent crises

  • Control anemia

  • Help with symptoms

Doctors treat sickle cell disease with:

  • Medicines

  • Folate, a vitamin that helps the body make new red blood cells

Sickle cell crisis usually requires an emergency department visit and may require a hospital stay. In the emergency department and hospital, doctors may give you:

  • Fluids in your vein (IV)

  • Pain medicine

  • Blood transfusions

  • Oxygen

  • Treatment for conditions that may have caused the crisis, such as an infection

Stem cell transplantation is a medical procedure that may cure sickle cell disease in some people, but it is very dangerous and so is used only in life-threatening situations. Stem cell or gene therapy may some day cure sickle cell disease safely.

How can I prevent sickle cell crisis and complications?

You should:

  • Avoid activities that lower the oxygen in your blood

  • See a doctor for all illnesses, even minor ones

  • Get vaccines

Doctors often have children with sickle cell anemia take penicillin from 4 months until 6 years old to help prevent infections that may cause a sickle cell crisis.

Where can I learn more about sickle cell disease?

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Test your knowledge

Polyglandular Deficiency Syndromes
Polyglandular deficiency syndromes are hereditary disorders in which several endocrine glands (ie, glands that secrete hormones) malfunction together. Which of the following is the most appropriate treatment for these types of disorders? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID