Aplastic crisis and sickle cell disease


What is an aplastic crisis?

An aplastic crisis occurs when the body does not make enough new red blood cells to replace the red blood cells that are circulating in the body. Children with sickle cell disease need to make a lot of new red blood cells. If a child with sickle cell disease stops making red blood cells for a few days, severe anemia (too few red blood cells) can result. This dangerous condition must be treated. If not, serious health problems can occur, including death.

What causes an aplastic crisis?

Usually, an aplastic crisis is caused by a virus. Parvovirus B19 (or Fifth’s Disease) is one of the most common causes. The virus causes the bone marrow to stop making new red blood cells for 7 to 10 days. Red blood cells carry oxygen to the body. New red blood cells are made in the bone marrow and then released into the body’s blood supply. Normally, the bone marrow is always making new red blood cells. During an aplastic crisis, the bone marrow stops making red blood cells for a short time. This is called transient (temporary) aplastic crisis. A transient aplastic crisis normally lasts between 7 and 10 days. Then, the bone marrow starts making red blood cells again.

In most people, this does not cause a problem because normal red blood cells last 90 to 120 days. However, in people with sickle cell disease, this is a serious problem because their red blood cells only last for 7 to 20 days. 

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

Often during an aplastic crisis, a child will have flu-like symptoms: fever, cough, and fatigue. However instead of improving, the child will keep getting worse. The child’s energy level will be low, and he will become even more tired and pale. If you think your child is having an aplastic crisis, call your child’s nurse case manager or after hours ask for the hematology doctor on call. If your child is having the following symptoms, take him to the emergency room right away:

  • Trouble breathing,
  • Non-responsive (cannot wake up),
  • Extremely pale, or
  • Lethargic (extremely tired)

Do not wait to talk to the nurse case manager or the hematology doctor, go to the emergency room. 

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

The staff will take a sample of your child’s blood and perform a complete blood count (CBC) and a reticulocyte count.

The CBC will let the doctor know your child’s hemoglobin level. People with sickle cell disease have abnormal hemoglobin called sickle hemoglobin (hemoglobin S). Hemoglobin is the part of the blood that carries oxygen. Sickle hemoglobin does not last as long as normal hemoglobin, so people with sickle cell disease tend to be anemic. A person with sickle cell disease becomes even more anemic during an aplastic crisis. Hemoglobin levels can decrease quickly during an aplastic crisis to dangerously low levels.

The reticulocyte count measures the number of young red blood cells in the blood. Reticulocyte is the name for a new red blood cell that is forming in the bone marrow. Normally, reticulocytes remain in the bone marrow until they develop into mature red blood cells. Then, they leave the bone marrow and move into the bloodstream. Usually a person with sickle cell disease has a high reticulocyte count. In an aplastic crisis, the reticulocyte count in a person with sickle cell disease may drop as low as zero.

The CBC and reticulocyte count are important tests to help find out how severe the anemia is and to decide the course of treatment. The hemoglobin level and reticulocyte counts will vary depending on the type of sickle cell disease and the person. Usually the doctor will monitor the CBC and reticulocyte count on a daily basis during an aplastic crisis. 

How is an aplastic crisis treated?

If the anemia becomes severe, your child may need to have a blood transfusion. The donor red blood cells will provide oxygen to the body until the bone marrow begins to make reticulocytes. While in the hospital, the staff will place your child in isolation (a room away from other patients). This is needed because parvovirus is contagious (can spread from person to person). People entering the room will have to wear a mask and a gown. The parvovirus is not dangerous to most people, but it can cause problems for pregnant women and other sickle cell patients.

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

Not usually. Once a child has had a parvovirus infection, he should be protected from having it again.

Does the family need to be careful?

Yes, parvovirus spreads easily. If you have other children with sickle cell disease, they should be checked by a doctor. 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 exposed to the virus, she should tell her doctor right away. 

Can an aplastic crisis be prevented?

No. In addition to parvovirus, many other viruses can cause an aplastic crisis. Children with sickle cell disease who are younger than 15 years are most likely to get parvovirus and have an aplastic crisis. While it is impossible to avoid viruses throughout childhood, there are ways to decrease your child’s chances of catching a virus.

What else can I do to control the spread of infection?

It is possible for people infected with the flu or another virus to infect others even before symptoms appear. To help prevent the spread of viruses, you should follow these good infection control practices all the times:

  • Clean your hands often with soap and water or with an alcohol-based hand sanitizer.
  • If you have to cough or sneeze, cover your face with your arm or a tissue. Then, throw the tissue away and clean your hands.
  • Avoid touching your eyes, nose, or mouth if you have flu-like symptoms; germs spread that way.
  • Get the pneumovax, H1N1, and seasonal flu vaccines as soon as they are offered each year. 


If you have questions please talk to a member of the hematology team. If your child is having an aplastic crisis, call your child’s nurse case manager or after hours call the main operator at (901) 595-3300 or toll-free 1-866-2STJUDE (1-866-278-5833) and ask for the hematology doctor on call. If you are unable to contact the nurse case manager or hematology doctor go to the emergency room.


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.

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