Aplastic Crisis

Why aplastic crisis happens

Normal red blood cells live about 120 days. In conditions such as sickle cell disease or hereditary spherocytosis, they may survive only 10 to 20 days. The bone marrow works constantly at high speed to keep up, so the person depends on non-stop production.

Parvovirus B19 infects and destroys the cells in the bone marrow that become red blood cells. In healthy people this pause lasts about a week and goes unnoticed, because existing red cells last long enough. In someone with short-lived red cells, hemoglobin can fall by half or more within days.

Causes

• Parvovirus B19, the virus that causes fifth disease (slapped cheek syndrome) in children: the cause of most cases
• other infections, less commonly: streptococcus, salmonella, Epstein-Barr virus
• some medicines and toxins, rarely

At-risk conditions include sickle cell disease, hereditary spherocytosis, hereditary elliptocytosis, thalassemia, G6PD deficiency, pyruvate kinase deficiency and autoimmune hemolytic anemia.

Symptoms

Symptoms develop over a few days, often after a mild viral illness with fever, headache and runny nose:

• unusual tiredness and weakness
• paler skin, lips and inner eyelids than usual
• shortness of breath and a fast heartbeat
• headache and dizziness
• in severe cases, heart failure, confusion or fainting

Notably, jaundice may decrease during the crisis, because fewer new red cells are being produced to break down. The classic slapped cheek rash is often absent in people with aplastic crisis.

Diagnosis

• Full blood count: a sharp drop in hemoglobin compared with the person's usual level.
• Reticulocyte count: very low or nearly zero, which is the hallmark. In normal hemolytic anemia it is high.
• Parvovirus B19 tests: IgM antibodies or viral DNA by PCR.
• Bone marrow exam: rarely needed; shows absence of red cell precursors with giant early cells.

Aplastic crisis vs other crises

Aplastic crisis is also different from aplastic anemia, which is a long-term failure of the bone marrow to produce all blood cell types.

Treatment

• Red blood cell transfusion to raise hemoglobin to a safe level. Most people with severe drops need one or more transfusions.
• Monitoring of hemoglobin and reticulocytes until recovery, usually seen as a rise in reticulocytes within 7 to 10 days.
• Supportive care: rest, fluids and fever control.
• Infection control: people with parvovirus B19 are contagious during the crisis, so hospitals use droplet precautions and keep them away from pregnant staff and other vulnerable patients.
• IV immunoglobulin is used for chronic parvovirus infection in people with weakened immune systems, not usually for a typical crisis.

Recovery and prevention

The marrow recovers once the immune system clears the virus, generally within 1 to 2 weeks. Infection usually gives lifelong immunity, so aplastic crisis from parvovirus rarely happens twice. There is no vaccine. Siblings with the same blood disorder may develop a crisis at the same time, so families should watch for symptoms. Good hand hygiene helps reduce spread.

Pregnant people exposed to parvovirus should contact their prenatal provider, as the virus can rarely cause severe anemia in the unborn baby.

Frequently asked questions

What causes aplastic crisis?

Most aplastic crises are caused by parvovirus B19, which temporarily stops red blood cell production in the bone marrow. It becomes dangerous in people with conditions that shorten red cell lifespan, such as sickle cell disease and hereditary spherocytosis.

How long does an aplastic crisis last?

Red cell production usually resumes within 7 to 14 days as the immune system clears the virus. Hemoglobin then recovers over the following weeks. A blood transfusion is often needed to bridge the gap safely.

Is aplastic crisis the same as aplastic anemia?

No. Aplastic crisis is a short-term halt in red blood cell production, usually caused by a virus, in people with hemolytic anemia. Aplastic anemia is a long-term bone marrow failure that reduces all types of blood cells and needs different treatment.

Can you get aplastic crisis more than once?

It is uncommon. Parvovirus B19 infection usually gives lifelong immunity. Repeat episodes are possible with other infections or in people with weakened immune systems, but most people have only one parvovirus-related crisis.