Multisystem Inflammatory Syndrome in Children (MIS-C)

What is multisystem inflammatory syndrome in children (MIS-C)?

Multisystem inflammatory syndrome in children (MIS-C), also called pediatric multi-system inflammatory syndrome (PMIS or PIMS), is a newly recognized, potentially serious illness in children that seems to be related to COVID-19. For many children, it appears to be a delayed complication of coronavirus infection, although not all children with MIS-C-related symptoms test positive for the virus.

MIS-C has varied symptoms that affect several organs and systems in the body. Many children have symptoms resembling toxic shock syndrome or Kawasaki disease, in which blood vessels, including the coronary arteries, enlarge or form aneurysms. Some children have signs of excessive blood clotting, gastrointestinal symptoms, kidney injury, neurologic symptoms, or heart inflammation with impaired heart function. These symptoms can occur in different combinations.

While Boston Children’s Hospital and other medical centers are still actively collecting data on MIS-C, it seems so far to be rare, and most children recover with careful observation and treatment. To date, some children with this syndrome have needed to be hospitalized, but only a very small percentage have passed away.

If you think your child might have MIS-C, consult with your primary care provider. Blood tests may be recommended, depending on your child’s symptoms. Children with MIS-C need close observation by pediatric specialists in infectious disease, rheumatology, critical care, and cardiology.

What are the signs and symptoms of MIS-C?

Because the illness is so new, symptoms are still being documented, and they may vary from child to child. The main thing to watch for is a persistent fever (lasting more than 24 hours and usually present for several days), your child appearing fatigued and ill, or loss of appetite or not drinking enough fluids. Symptoms can get worse quickly, so seek timely medical attention if you see anything concerning.

Specific features of MIS-C may include:

  • Kawasaki-like symptoms: Rash, bloodshot eyes, swollen hands and feet, cracked lips, a swollen tongue that looks like a strawberry, and an enlarged lymph node in the neck. (More on Kawasaki disease)
  • Toxic shock-like symptoms: Severe flu-like symptoms with high fever, as well as a sunburn-like rash, low blood pressure, and a very high heart rate. (More on toxic shock syndrome)
  • Gastrointestinal symptoms: diarrhea, vomiting, abdominal pain, or a swollen abdomen.
  • Respiratory symptoms that have been reported with COVID-19, such as persistent cough and shortness of breath, may or may not be present.

How is multisystem inflammatory syndrome in children diagnosed?

Currently, MIS-C is diagnosed based on symptoms (persistent fever and dysfunction of one or more organs, such as the heart or kidneys), together with laboratory tests to look for signs of inflammation in the body.

Children should also have a positive test for COVID-19 or have been exposed to the virus within the past four weeks, although neither is absolutely necessary to make a diagnosis. Testing is also done to rule out other possible causes of the symptoms, such as other infections.

Once MIS-C is diagnosed, children will need to be followed over time with laboratory tests to assess inflammation, blood clotting, liver function, heart function, and other aspects of their illness. Children should also have echocardiograms to evaluate their heart and coronary arteries.

Treatment of multi-system inflammatory syndrome in children

Children who appear to have MIS-C need close observation. Some will need to admitted to the hospital, and a small number may need intensive care. Pediatric specialists in infectious disease, rheumatology, critical care, and cardiology can anticipate and address different aspects of the illness.

Treatments currently include anticoagulation to curb blood clotting, IV immunoglobulin (used to treat Kawasaki disease), and anti-inflammatory drugs (corticosteroids, and drugs blocking IL-1 or IL-6). Other treatments may be used depending on the results of laboratory tests.

Children with serious cardiac complications will need to be followed over time, with repeat echocardiograms to monitor their heart and coronary arteries.

What causes multi-system inflammatory syndrome in children?

The cause of MIS-C is not yet fully understood — it’s a question that’s being actively investigated, here at Boston Children’s and elsewhere.

Some researchers suspect that MIS-C is caused by a delayed immune response to the coronavirus that somehow goes into overdrive, causing inflammation that damages organs. It’s also possible that the antibodies children make to the virus are creating the immune reaction. Since only a small number of children develop MIS-C, it is possible that there are genetic factors that make some children susceptible.

It is important to remember that overall, children fare very well with COVID-19 as compared to adults. Only a small number of children seem to develop signs and symptoms of MIS-C, and most have recovered quickly.