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Aplastic crisis


What is an aplastic crisis?

An aplastic crisis is when the body does not make enough new red blood cells to replace the ones that are already in the blood. Normally, the soft tissue at the center of your bones, called bone marrow, constantly makes new red blood cells. These cells go into your blood supply and carry oxygen through the body.

Your child needs to make a lot of new red blood cells if they have sickle cell disease. But during an aplastic crisis, the bone marrow stops making red blood cells for a short time. This is called transient (temporary) aplastic crisis. It normally lasts 7 to 10 days. Then the bone marrow starts making red blood cells again.

An aplastic crisis is not a problem for most people, because normal red blood cells last 90 to 120 days. But it is a serious problem in people who have sickle cell disease. Their red blood cells only last for 7 to 20 days. So if your child with sickle cell stops making red blood cells for a few days, they can get severe anemia (too few red blood cells).

An aplastic crisis is a medical emergency. Your child needs treatment to avoid serious health problems, including death.

What causes an aplastic crisis?

Usually a virus. Parvovirus B19 is one (1) of the most common causes. “Fifth’s disease” is another name for it. This virus causes the bone marrow to stop making new red blood cells for 7 to 10 days.

How will I know if my child is having an aplastic crisis?

Your child might have a fever and cough, and be very tired. They might act like they have the flu. However, they will get worse each day instead of better. Their energy level will be low, and they will look tired and pale.

When to call the doctor or nurse

If you think your child is having an aplastic crisis, call your child’s nurse case manager. After regular office hours, ask for the hematology doctor on call.

Take your child to the emergency room right away if they:

  • Have trouble breathing,
  • Cannot wake up,
  • Look extremely pale, or
  • Act extremely tired.

Do not wait to talk to the nurse case manager or the hematology doctor if you see these signs. Go to the emergency room. And always call 911 if your child has a medical emergency and needs help right away.

How will the doctor know if my child is having an aplastic crisis?

The staff will take a sample of your child’s blood. They will do 2 tests, a complete blood count (CBC) and a reticulocyte count.

What the CBC tells your child’s doctor

The CBC tells the doctor your child’s hemoglobin level. Hemoglobin is the part of the blood that carries oxygen. People with sickle cell disease have abnormal hemoglobin called sickle hemoglobin (hemoglobin S). It does not last as long as normal hemoglobin, so people with sickle cell disease have too little hemoglobin in their blood. A person with sickle cell disease becomes even more anemic during an aplastic crisis. Hemoglobin levels can go dangerously low during an aplastic crisis.

What the reticulocyte count tells your child’s doctor

The reticulocyte count tells the doctor how many young red blood cells there are in the blood. A reticulocyte is a new red blood cell that is forming in the bone marrow. Normally, reticulocytes stay in the bone marrow until they become mature red blood cells. Then they leave the bone marrow and move into the bloodstream. A person with sickle cell disease usually has a high reticulocyte count. In an aplastic crisis, the reticulocyte count can go as low as zero.

Knowing your child’s CBC and reticulocyte counts tells the doctor how severe the anemia is. This helps them decide on treatment. The doctor will probably check your child’s CBC and reticulocyte count every day during an aplastic crisis.

How is an aplastic crisis treated?

Your child might need a blood transfusion if they have severe anemia. The donated red blood cells will give the body oxygen until the bone marrow starts making reticulocytes again.

Your child will go into isolation during treatment. This means a room away from other patients. This is needed because parvovirus can spread from person to person. It is not dangerous to most people, but it can cause problems for pregnant women and other people with sickle cell disease. People who come into your child’s room must wear a mask and a gown.

Can a child have more than one (1) aplastic crisis?

Not usually. Once a child has had a parvovirus infection, they rarely get it again.

Does the family need to be careful?

Yes. Parvovirus spreads easily. Your doctor should check any other children in your family who have sickle cell disease. Pregnant women should stay away from a child who is having an aplastic crisis, because the virus can harm an unborn baby. If a pregnant woman has been near someone who has parvovirus, she should tell her doctor right away.

Can an aplastic crisis be prevented?

No. Other viruses besides parvovirus can cause an aplastic crisis. Children under 15 with sickle cell disease are most likely to get parvovirus and have an aplastic crisis. It is impossible for your child to avoid every virus, but you can do things to lower their chances of getting one.

What can I do to keep viruses from spreading?

You can help keep viruses from spreading by doing the following things.

  • Clean your hands often. Use soap and water or an alcohol-based hand sanitizer.
  • Cover your face if you cough or sneeze. Use your arm or a tissue. Throw the tissue away and clean your hands.
  • Avoid touching your eyes, nose, or mouth if you have flu-like symptoms. You could get germs on your hands and spread them by touching other things.
  • Get the seasonal flu vaccine as soon as it is available each year. Get the pneumovax, H1N1, and other vaccines on the correct schedule.

These things are important because you can spread a virus even before you start feeling sick.


Please talk to a member of the hematology team if you have questions. Call the clinic at 901-595-5041 Monday through Friday 7:30–5 p.m. After 5 p.m. or on the weekends, call 901-595-3000 and ask to speak to the hematologist on call.

You may also call the main St. Jude operator at 901-595-3300 or toll-free 1-866-2STJUDE (1-866-278-5833).

Take your child to the emergency room if you cannot reach someone on the hematology team or the hematology doctor.


This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.

St. Jude complies with health care-related federal civil rights laws and does not discriminate on the basis of race, color, national origin, age, disability, or sex.

ATTENTION: If you speak another language, assistance services, free of charge, are available to you. Call 1-866-278-5833 (TTY: 1-901-595-1040).

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