For a stretch last spring, national headlines were dominated by the disturbing news that children — who’d previously been thought to be largely spared by the most dangerous symptoms of COVID-19 — were coming down with a rare inflammatory syndrome several weeks after they’d been exposed to the virus. Hundreds of children were hospitalized. Several died.
Then multisystem inflammatory syndrome in children (or MIS-C as it is often called) just sort of slipped out of the national news cycle. The syndrome is rare, and so far has been concentrated in areas like New York, once the epicenter of the pandemic domestically.
But now, as COVID-19 surges elsewhere in the United States, experts warn more cases will likely occur — while school districts and parents grapple with how to re-open schools amid an ongoing pandemic.
Fortunately, doctors and researchers have been racing to better understand the mysterious syndrome, which can cause life-threatening complications including coronary-artery aneurysms and toxic shock syndrome.
Here is some of what we know — and what we still don’t know — so far.
Why some kids get MIS-C remains a total mystery.
There is now a fairly broad consensus that MIS-C is a strong immune system response to SARS-COV-2, the virus that causes COVID-19. That response generally develops about two to four weeks after the initial infection, and can lead to inflammation in several (or all) of a child’s internal organs. And that can be serious. Two studies, both recently published in the New England Journal of Medicine, which looked at New York-based children who developed MIS-C in the spring, found that roughly 80 percent required intensive care.
Experts have learned a few things about who gets this syndrome. There may be a slightly higher proportion of cases among Black and Latino children than white children.
Beyond that, however, experts still simply do not know why some kids get MIS-C and others don’t.
“We don’t know the risk factors — which kids get this and which kids don’t, it’s hard to know. Especially because most have been previously healthy,” said Dr. Nadine Choueiter, a pediatric cardiologist and director of the Kawasaki Disease program at the Children’s Hospital at Montefiore in New York City.
“We don’t have answers yet,” she added.
It’s rare, but it is hard to say just how rare.
Experts agree that MIS-C is an uncommon outcome, but just how uncommon is really unclear at this point — in large part because we simply don’t have good data on how many kids have been infected with COVID-19.
There have been some recent efforts to get a handle on how widespread (or not) MIS-C is. For example, an editorial accompanying those two recent studies on MIS-C in the New England Journal of Medicine cited estimates that MIS-C affects 2 in 100,000 people under the age of 21, while COVID-19 has been diagnosed in roughly 320 per 100,000 similarly aged people during the same time.
“What we’re going to start seeing, I’m sure — now that they’re having peaks in Texas, Florida and California and other states — is that they’re going to start seeing more of the syndrome there.”
Again, however, it is simply too soon to estimate with any real certainty.
“I think we can say that the most severe manifestations, the ones that end up in the hospital, seem to be rare,” said Dr. Roberto Posada, a pediatric infectious disease doctor and co-author of a recent study on 15 children who were treated for MIS-C at Mount Sinai Kravis Children’s Hospital in New York City.
There isn’t a universal treatment, but outcomes have been pretty good.
Part of what made MIS-C so unsettling early on is that doctors simply hadn’t seen it before, so they weren’t sure exactly what they were treating. Doctors still have many questions about the syndrome’s origins and the most effective treatment, but the majority of children fare pretty well.
“The treatment varies between different centers, in different parts of the world, yet the majority improve,” said Choueiter, who said that a doctors’ task when a child comes in really sick with MIS-C is to support their organs. “If you look at the literature, up to 97 percent of children leave the hospital with normal heart function.” She added that doctors like herself are tracking patients over time to see if the syndrome has any long-term effects.
“The initial presentation can be very alarming, but most of them recover OK after a few days in the hospital,” echoed Posada, who also added that doctors have likely gotten better at spotting early signs of this syndrome now that they have known about it for several months.
We could start seeing more cases elsewhere in the country.
“What seems to happen is that cases follow the peak in COVID activity among the general population by about three weeks or so, so in the New York City area we saw the peak in COVID cases in April, and we started seeing this syndrome in children in late April and early May,” said Posada. “What we’re going to start seeing, I’m sure — now that they’re having peaks in Texas, Florida and California and other states — is that they’re going to start seeing more of the syndrome there.”
In the small recent study from Mount Sinai in New York City, most of the children who tested positive for COVID-19 antibodies were asymptomatic, so their families hadn’t realized they had the virus. A few had mild symptoms. In other words, it is not as though these children were clearly very sick with COVID-19, then went on to develop this subsequent disease. They all seemed pretty healthy.
That’s why it is imperative that parents be aware of the symptoms associated with MIS-C, rare though it may be. Fever is a big one, Posada emphasized, especially if it lasts for more than three days. Other possible signs include abdominal pain, vomiting and diarrhea, a rash, and bloodshot eyes.
If you have any concerns, reach out to your child’s pediatrician. If it seems serious, go to an emergency room right away, Posada urged.
“I [recently] saw a patient, a toddler, who had a fever for five days, but otherwise didn’t look that sick. Usually, I would probably say, ‘Go home. Let’s see what happens tomorrow or the day after.’ But we’re being more conservative these days,” he said. “We admitted that child to the hospital.”