Understanding MIS-C: A rare, COVIDrelated condition in kids is on the decline
A UPMC doctor recalls his MIS-C patients as ‘[s]ome of the sickest kids in the building.’
There are no mild cases of Multisystem Inflammatory Syndrome in Children, or MIS-C.
“It’s as subtle as a sledgehammer to the forehead,” explains Tyler Harris, a pediatric cardiologist and newly appointed director of the Cardiac Exercise Laboratory at the UPMC Children’s Hospital of Pittsburgh.
MIS-C is a rare but severe condition that develops in children two to six weeks after a COVID-19 infection.
And while case numbers are in overall decline, per a Centers for Disease Control and Prevention report released earlier this year, instances do still pop up when rates of the virus spike, as they did in the fall of 2023.
Coronavirus can affect almost every organ in the body, including the heart, lungs, kidneys, skin and digestive system. When the body’s immune system detects an invader, such as the COVID virus, it triggers inflammation.
To understand inflammation, think of when you get a cut on your finger. Inflammation causes blood vessels to expand, making the area red and warm. White blood cells then rush in to attack germs and clear away damaged cells. This might cause swelling and pain, but it’s a sign that the body is working to heal the cut. Over time, as the danger from infection passes and healing progresses, inflammation dies back, and your finger feels better.
In children with MIS-C, however, the immune system kicks into overdrive and begins to attack the same organs it initially tried to protect from COVID, leading to inflamed organs, prolonged high fevers, diarrhea, vomiting and rashes. Doctors don’t understand why MIS-C targets some children and not others, nor is it clear why the immune system goes into overdrive after the COVID-19 infection is cleared away.
By definition, MIS-C requires hospitalization. Harris had a front-row seat to the emergence of this new syndrome during the pandemic, and he witnessed the havoc MIS-C inflicted on children.
“They were really, really, really sick kids,” he remembers. “Some of the sickest kids in the building.”
A range of 200-399 MIS-C cases in Pennsylvania have been reported as of April 29, per the Centers for Disease Control and Prevention. Exact case numbers aren’t used for privacy, per the CDC.
Although most children make a full recovery, in a small number of cases, MIS-C is fatal.
The best protection against MIS-C is vaccinatingchildren against COVID-19.
In 2023, there were 117 reported cases of MIS-C. This is a 98% decrease from the peak incidence rate observed early in the pandemic (October 2020-April 2021). Most of these cases were in unvaccinated children.
Harris has not seen a case in Pennsylvania in over a year. He attributes the lack of cases to the vaccine and the fact that, by now, it is rare to find a child who hasn’t had COVID.
Children are at greatest risk for MISC during their first exposure to a COVID infection. If a child does not develop MIS-C the first time they encounter the virus, it is unlikely they will with subsequent exposures.
The CDC recommends staying up-todate with COVID-19 vaccines as the best way to prevent MIS-C. It also encourages parents and caregivers to discuss vaccinations and other prevention tools, such as practicing good hygiene and taking steps for cleaner air, with their child’s pediatrician and other health care professionals.
Harris agrees that vaccinating kids against COVID (and other preventable diseases) is exceedingly important. For those concerned about vaccine safety, Harris shares that he has treated 15 times more children for MIS-C than for COVID-19 vaccine-related side effects.
“You are much more likely to get side effects from getting COVID-19 than you are from getting the vaccine,” Harris emphasizes.
Although most kids fully recover, MIS-C is a new condition that developed alongside COVID-19, and researchers and doctors don’t fully understand the long-term repercussions of the syndrome.
“[Children with MIS-C] require a lot of medicine, a lot of medicines with side effects, and a lot of time in intensive care units,” Harris says. “It’s not just a cold. It’s a pretty severe illness, and one I would prefer not to have to treat.”