Experts have reported a strange new disease with ties to COVID-19 affecting children across the country. Learn the diagnostic symptoms of multisystem inflammatory syndrome (MIS-C) and the latest information from the CDC. 

By Nicole Harris
Updated May 27, 2020

For months, news reports have claimed that the coronavirus (COVID-19) mostly spared children. But now the Centers for Disease Control and Prevention (CDC) has issued a health alert for a strange new illness striking people under the age of 21 dubbed multisystem inflammatory syndrome in children (MIS-C)—and experts believe it has a link to COVID-19.

First reported on April 26, 2020, in the United Kingdom, MIS-C resembles toxic shock syndrome and the rare Kawasaki disease. There's been 176 reported cases in New York, where at least three children died from it. The patients were 5, 7, and 18 years old. More than 26 states—including New Jersey, California, Ohio, Georgia, and Michigan—and some European countries have also reported instances of MIS-C.  

Here's what we know so far about the symptoms of multisystem inflammatory syndrome in children, including the latest guidelines from the CDC to protect kids.

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Children with multisystem inflammatory syndrome are testing positive for COVID-19.

The New York City Department of Health studied 15 patients with MIS-C before May 4. It reported that, out of the 15 patients it studied, four had a positive coronavirus test. Of the remaining 11 patients, six tested “positive by serology,” meaning they had coronavirus antibodies, says Demetre C. Daskalakis, M.D., MPH, deputy commissioner of the New York City Health Department's Division of Disease Control. This suggests those patients might’ve been previously infected with the coronavirus. Doctors are also seeing positive COVID-19 tests or the presence of antibodies with new MIS-C cases. They believe the illness usually appears 4 to 6 weeks after COVID-19 exposure.

Symptoms of MIS-C are different from COVID-19.

Experts are still learning about MIS-C, so the full range of symptoms isn’t yet understood. However, the New York City Department of Health found some tell-tale signs. “All patients had subjective or measured fever and more than half reported rash, abdominal pain, vomiting, or diarrhea,” according to Dr. Daskalakis  in a letter to colleagues. Less than half of the patients experienced respiratory symptoms.

The CDC released the following diagnostic criteria for MIS-C: fever of 100.4 degrees or higher for at least 24 hours; evidence of inflammation; the need for hospitalization; involvement of at least two organs; and no alternative plausible diagnoses. The patient must also test positive for the coronavirus or its antibodies, or have had exposure to COVID-19 within the last four weeks. 

Note that cases appear to occur in those younger than 21, but the CDC notes it’s possible that adults could develop it too.

MIS-C can sometimes be severe.

Most children fully recover from MIS-C, but at least three children died from it so far. Others have suffered severe complications. “Patients with this syndrome who have been admitted to pediatric intensive care units (PICUs) have required cardiac and/or respiratory support,” says Dr. Daskalakis. The health department suggests, however, that only severe cases may have been studied. 

MIS-C is most likely not a form of Kawasaki Disease.

Kawasaki disease is a rare condition that causes inflammation (swelling and redness) in the blood vessels. It mainly affects infants and young children, says Michael Chang, M.D., an infectious disease pediatrician at McGovern Medical School at UTHealth in Houston. Doctors believe it’s caused by an immune system overreaction to an unknown trigger. 

So is MIS-C a form of Kawasaki disease? Experts say probably not. Most doctors believe that MIS-C is actually a separate condition caused by an abnormal immune response to COVID-19. Dr. Chang points out one major reason: Kawaksaki disease shares similar symptoms to MIS-C, but there are also large differences. What’s more, some adults are also experiencing an immune system overreaction to COVID-19, he says. 

According to  Daniel J. Penny, M.D., chief of cardiology at Texas Children’s Hospital, "What's becoming apparent is that the onset of this Kawasaki-like syndrome in a community appears to lag behind the appearance of COVID-19, which supports the idea that it is not the infection itself, but rather the body’s response to the infection." He says that the incidence of Kawasaki disease in Japan, which usually has the highest number of cases, does not appear to have increased during the coronavirus pandemic. "This could potentially mean the precise genetic mechanisms which predispose to usual Kawasaki disease may differ from those for COVID-associated Kawasaki disease," he says.

If your child has a persistent high fever, see a doctor.

Does your child have persistent fever, skin rash, vomiting, or other symptoms related to MIS-C? If he’s under 21, Dr. Daskalakis says to report it to the health department immediately, even if he has received a negative coronavirus test. Your child’s doctor will refer him to a "specialist in pediatric infectious disease, rheumatology, and/or critical care," says Dr. Daskalakis. Early diagnosis can ward off severe complications like organ damage. 

“If your child has a high fever that has gone on for more than three to five days without reason, you need to have your child assessed," emphasizes Lolita McDavid, M.D., professor of general pediatrics and adolescent medicine at Case Western Reserve University. Even if it’s not multisystem inflammatory syndrome, “it could be strep throat or something else that needs treatment,” she adds. 


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