Updated on December 19, 2024.
Since COVID-19 infections began spreading in the United States in early 2020, millions of children have tested positive for the illness. Many more have likely had the virus at some point, whether or not they’ve tested positive.
For most kids, a COVID infection causes mild symptoms. They typically recover after spending a week or two at home. But a small number may go on to develop multisystem inflammatory syndrome in children (MIS-C), a serious condition that can lead to severe illness, hospitalization, and even death.
One of the best ways to protect children from MIS-C is to have them vaccinated for COVID, and then stay current on the latest vaccines. Most reported cases of MIS-C have involved kids who were unvaccinated, partly vaccinated, or not up to date on vaccinations.
The good news is that MIS-C cases have dropped drastically since their early 2021 peak, from a few hundred to a small handful each week. Still, given its potential for harm, it’s important to learn about and understand this potentially serious illness.
MIS-C warning signs
Like its name implies, multisystem inflammatory syndrome in children is a condition associated with inflammation in at least two different parts of the body—the heart, lungs, kidneys, brain, skin, eyes, or organs of the digestive system. The first cases linked to COVID infection were reported in April 2020.
Experts do not know exactly what causes MIS-C, but it’s clear that it’s linked to a recent infection with COVID. “What we understand about it is that it’s probably a spectrum of COVID-related disease with severe inflammation,” says Dr. Ramirez. “It’s probably an inflammatory response to the virus.”
MIS-C is rare. When it happens, it typically occurs within two months of a COVID infection. A 100.4°F (38°C) fever that continues for at least 24 hours is often the first symptom. Other common symptoms include:
- Bloodshot or red eyes
- Skin rash
- Swelling or redness in the tongue or lips
- Swelling or redness in the hands or feet
- Belly pain, diarrhea, or vomiting
- Dizziness due to low blood pressure
- Heart problems
- Blood clots
- Shock
If your child experiences swelling or redness in the tongue or lips, heart problems, blood clots, or shock, call 911.
Otherwise, reach out to a healthcare provider right away if your child has a fever, has at least two of these symptoms, and was exposed to COVID during the previous two months.
“Any time parents are concerned about high fevers or any of these sorts of symptoms, they should bring it up to their physician as soon as they can and make sure that they mention if there’s been an exposure to COVID, or a potential exposure,” says Kacy Ramirez, MD, an associate professor of pediatric infectious diseases at Wake Forest University School of Medicine in Winston-Salem, North Carolina.
Keep in mind the following, additional warning signs of a medical emergency that require immediate attention:
- Trouble breathing
- Chest pain or pressure that does not go away
- Confusion or unusual behavior
- Pale, gray, or bluish skin, lips, or nail beds (depending on skin tone)
- Drowsiness or trouble waking
- Severe belly pain
If your child develops one or more of these serious symptoms, call 911.
How MIS-C is diagnosed
Some signs of MIS-C can be confused with other childhood illnesses. So, to make a diagnosis, healthcare providers need to rule out other possible causes, like bacterial infections. Children must also have tested positive for COVID recently, have antibodies to the coronavirus (which would indicate that they were infected in the past and recovered), or have a history of exposure to an infected person within two months of when their symptoms started.
It can be confusing, because some children develop MIS-C symptoms without having had obvious signs of an initial COVID infection. They may have mild COVID symptoms, or none at all. But they then develop MIS-C two to eight weeks later.
Reaching an MIS-C diagnosis depends on the whole picture—the child’s symptoms and signs, history, and bloodwork. Healthcare providers might also look at urine tests, or perform chest x-rays, ultrasounds, computed tomography (CT) scans, or echocardiograms to look for signs of MIS-C or inflammation.
Most kids diagnosed with MIS-C have been between the ages of 5 and 11. In the U.S., Hispanic/Latino and Black children have been disproportionately affected. This could reflect structural health disparities, medical distrust, or differences in genetic susceptibility. Another factor: COVID is more common in these communities.
How MIS-C is treated
Most children diagnosed with MIS-C are sick enough to be hospitalized, explains Ramirez.
Because the disease can strike so many organ systems, treatment typically requires a team of medical professionals. In addition to supportive care, such as intravenous (IV) fluids, treatment typically includes intravenous immunoglobulin (a drug that contains antibodies), steroids, antibiotics, treatments for clotting, and, in some cases, anti-inflammatory drugs ordinarily used to treat autoimmune disease. Kids may also need oxygen if they are having trouble breathing, or even a ventilator. If their blood pressure is low, they may need to take blood pressure medicine.
Most children with MIS-C feel better over time, with symptoms easing within two weeks. Still, they’ll need to be monitored over at least six months after they leave the hospital to make sure their heart and arteries are recovering well from the illness.
More research is necessary to fully understand long-term health effects that may be caused by MIS-C. The best way to protect a child against MIS-C and other complications is to make sure they stay up to date on COVID vaccinations.
