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Millions of children in the United States have gotten COVID-19 since the pandemic began.

Most children who do get COVID-19 are asymptomatic or have mild symptoms. But some have developed a rare complication called multisystem inflammatory syndrome in children (MIS-C).

Reports of the condition in children began in the spring of 2020.

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What Is MIS-C?

MIS-C is a rare condition that can cause inflammation in several different parts of a child’s body, including:

  • Heart
  • Lungs
  • Liver
  • Brain
  • Skin
  • Eyes
  • Gastrointestinal organs

The inflammation happens as the immune system’s response to a prior infection with SARS-CoV-2, the virus that causes COVID-19.

MIS-C can cause serious, even life-threatening problems. But most children who have had MIS-C eventually recovered with treatment.

“This has been a completely new entity,” says Tyler Harris, pediatric cardiologist, UPMC Children’s Hospital of Pittsburgh. “We’ve had to figure out what it is, how to treat it, how to counsel families, and how to manage it.”

Dr. Harris says according to data, 1 in 3,000 to 10,000 children get MIS-C after having COVID-19.

MIS-C Symptoms

One of the most common symptoms of MIS-C is a constant fever for more than five days. Other typical symptoms may include:

  • Stomach pain.
  • Bloodshot eyes.
  • Vomiting and diarrhea.
  • Trouble breathing.
  • Skin rash.
  • Muscle and joint pain.

Not all children will have the same symptoms. But if your child has an ongoing fever for more than four to five days and one or more of the above symptoms, call their doctor.

MIS-C also can cause some severe, life-threatening symptoms. Call 911 or go to the nearest Emergency Department if your child has these symptoms or others that you’re concerned about:

  • Trouble breathing.
  • Ongoing chest pain or pressure.
  • Pale or gray skin, lips, or nails.
  • Confusion.
  • Problems waking up or staying awake.

MIS-C vs. Kawasaki disease

MIS-C has symptoms similar to those of Kawasaki disease, a rare childhood inflammatory illness sometimes related to infections.

However, there are differences between Kawasaki disease and MIS-C. For example, MIS-C typically affects older children than Kawasaki disease. Children with MIS-C also are more at risk for certain symptoms, including:

  • Low blood pressure.
  • Gastrointestinal symptoms.
  • Lymphopenia (low levels of lymphocytes, a type of white blood cell).
  • Thrombocytopenia (low blood platelet count).

The effects on the heart also differ between MIS-C and Kawasaki.

“When MIS-C came along, it looks similar to Kawasaki’s in lots of ways,” Dr. Harris says. “In other ways, it looks very different.”

MIS-C and myocarditis

When children have MIS-C, it causes inflammation in the heart called myocarditis. MIS-C is one of many causes of myocarditis.

Myocarditis can lead to abnormal heart rhythms (arrhythmia), decreased heart function, and potentially death if the heart is stressed. Treatment includes medication and exercise restriction until the inflammation heals.

MIS-C Diagnosis and Treatment

When MIS-C first emerged, not much was known about it. But the similarities with Kawasaki disease provided a baseline of knowledge, Dr. Harris says. And since 2020, knowledge has improved on how to treat the condition.

To diagnose MIS-C, doctors may use blood tests, an echocardiogram, or x-rays.

Because MIS-C can affect several different organs, your child’s care team may include many different specialists.

Treatment will attempt to reduce inflammation and prevent organ damage. Potential treatments for MIS-C may include:

  • Intravenous immunoglobulin (IVIG).
  • Glucocorticoids or other steroids.
  • Other anti-inflammatory medication.

Depending on their symptoms, your child also may need other supportive therapies. This may include fluids, breathing support, and more. Treatment for MIS-C should take place in the hospital as children are very ill with it. Some cases may require care in the pediatric intensive care unit.

Although MIS-C can be serious, quick treatment helps most children recover.

“I think over the course of the last two years, we’ve gone from not knowing what it is and what to do, to really at this point having fairly robust treatment protocols and guidelines,” Dr. Harris says.

Can I Prevent MIS-C?

According to the Centers for Disease Control and Prevention (CDC), much is still unknown about MIS-C. That includes why some children get it and some children don’t, as well as whether some children may be more at risk.

Because MIS-C is caused by COVID-19, preventing COVID-19 can help prevent MIS-C.

One key way to prevent COVID-19 is by getting vaccinated. Children 6 months and older are now eligible to receive the COVID-19 vaccine.

According to a CDC study from January 2022, COVID-19 vaccination can have a significant impact in reducing the risk of MIS-C. The study reported COVID-19 vaccination reduced the risk of MIS-C by 91% in children between 12 and 18 years old. Of children hospitalized with MIS-C, 95% were unvaccinated.

No vaccinated child required life support, the study reported.

“We do have some data that have shown that vaccination reduces MIS-C significantly,” Dr. Harris says. “Most of the people that were getting MIS-C were unvaccinated, and the people that were getting very, very sick with MIS-C were unvaccinated. So it appears the vaccine is very protective for MIS-C.”

The CDC study took place before children ages 5 to 11 were eligible for vaccination. It also took place before the emergence of the more transmissible Omicron (B.1.1.529) variant. However, new data shows less MIS-C with the Omicron variant, possibly due to vaccination. Scientists are continuing to study the effectiveness of COVID-19 vaccination, including in preventing complications like MIS-C.

In addition to vaccination, other steps to help prevent MIS-C include:

  • Wearing a facemask. Children 2 and older should wear a facemask indoors in public in communities where COVID-19 spread is high, even if they are vaccinated. If your child is unvaccinated, you should consider having them wear a mask in indoor public areas in all situations.
  • Physical distancing. If your child is not fully vaccinated, or if you live in a community with high COVID-19 spread, maintain a physical distance of 6 feet from people not from your household while in indoor public places.
  • Avoid crowds. Stay away from poorly ventilated indoor places and areas with large numbers of people.
  • Get tested. If your child is showing symptoms of COVID-19 or has been exposed to someone with COVID-19, talk to their doctor about getting them tested.
  • Hand hygiene. Have your child wash their hands regularly with soap and water, scrubbing for at least 20 seconds before rinsing. If soap and water are unavailable, use a hand sanitizer with at least 60% alcohol.

We are still learning more about MIS-C and COVID-19 as the pandemic continues. For more information about COVID-19 from UPMC Children’s, visit our website.

Editor's Note: This video was originally published on , and was last reviewed on .

Sources

Please place each source on it's own line, using the following HTML markup:

American Heart Association, What Is Kawasaki Disease? Link

Ariana Eunjung Cha and Chelsea Janes, Children Are Falling Ill With Perplexing Inflammatory Syndrome Thought to Be Linked to COVID-19. The Washington Post. Link

Maria Godoy. Mystery Inflammatory Syndrome In Kids And Teens Likely Linked To COVID-19. NPR. Link

Andrew Jacobs and Edgar Sandoval, Mysterious Coronavirus Illness Claims 3 Children in New York. The New York Times. Link

New York Department of Health, Health Advisory: Pediatric Multi-System Inflammatory Syndrome Potentially Associated With Coronavirus Disease (COVID-19) in Children. Link

Royal College of Paediatrics and Child Health, Guidance: Paediatric Multisystem Inflammatory Syndrome Temporally Associated With COVID-19. Link

About Pediatrics

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