This New Covid-19-Related Disease Strikes Children

Some children exposed to the coronavirus that causes Covid-19 develop a dangerous inflammatory condition called MIS-C. Here's what doctors want you to know.

The virus that causes Covid-19 is still circulating and infecting people at record levels. On July 1st alone, Florida recorded almost 10,000 cases. Though many cases are mild, the virus can be severe, even deadly—particularly for people with chronic health conditions or other risk factors.

So far, children have not been hit particularly hard by the virus, says Jessica Mouledoux, MD, a pediatric cardiologist with the Ochsner Hospital for Children in New Orleans. Or at least, that was what experts thought: Now a number of children exposed to the virus that causes Covid-19 have developed bizarre and potentially deadly inflammation of limbs and organs—including the brain, heart, lungs, and kidneys—and doctors are scrambling for ways to spot the condition early and treat it effectively.

This Covid-19 syndrome is rare

The illness—now known as multi-system inflammatory syndrome in children (MIS-C)—was first flagged by the U.K. Paediatric Intensive Care Society on April 27. However, a recent Los Angeles Times article raises the possibility that mysterious deaths among children back in December 2019 may be attributable to MIS-C.

Cases have since been reported in continental Europe and elsewhere. Fortunately, the syndrome is rare, reports Kwang Sik Kim, MD, director of pediatric infectious diseases and professor of pediatrics at Johns Hopkins Medicine in Baltimore.

In one analysis of the condition, the Centers for Disease Control and Prevention (CDC) went through medical records from 26 states and found that between March 15 and May 20, there were 186 children with MIS-C: 62 percent were boys, 38 percent girls. The hardest-hit ages were kids between five and 14 and they accounted for half of all cases; infants and toddlers made up a third of the total.

The link to Kawasaki disease

Initially, doctors believed MIS-C might be another rare inflammatory condition that strikes very young children: Kawasaki disease (KD). First recognized in 1967, KD causes inflamed or swollen blood vessels throughout the body. It typically affects children under the age of five and its defining symptom is a fever (usually over 101°F) for at least four days, explains Guliz Erdem, MD, an infectious disease physician at Nationwide Children’s Hospital in Columbus, Ohio.

Other symptoms can include a rash, swelling of the hands, feet, and neck, as well as redness in the eyes, lips, and inside of the mouth. Most kids recover, but about 5 percent go on to develop Kawasaki disease shock syndrome, which can lead to heart problems. No one knows what causes KD, but it may be triggered by an underlying respiratory tract infection, says Dr. Erdem.

mother taking daughter's temperature at home sickKelly Sikkema/Unsplash

What we know about MIS-C

So far, the new syndrome seems to have features of both Kawasaki disease and toxic shock, says Dr. Kim. It’s more common in older children: While KD primarily strikes children younger than five, the CDC report found that 65 percent of the MIS-C cases were in children five and older (16 percent were in teens between the ages of 15 and 20). MIS-C hits kids of Hispanic, Latino, and African descent hardest, where KD is more prevalent in children of Japanese and Korean heritage. (However, no documented cases of MIS-C have been reported in Asia.)

“Part of MIS-C looks like Kawasaki disease, part of it looks like what we call macrophage activation syndrome which is an intense cytokine release [an overreaction by the immune system] and part of it is we don’t know,” Dr. Ergem says. “It’s most likely a combination of all of that.” Different children have different symptoms; plus, MIS-C has similarities to the “cytokine storm” immune response that occurs in some adults with Covid-19, often when it seems they’re already recovering.

The Covid-19 connection

Some researchers are still trying to establish a firm link between Covid-19 and MIS-C, but it’s probably just a matter of time, says Dr. Kim. In June, British researchers published a study of 58 children with MIS-C in the Journal of the American Medical Association (JAMA). The researchers found that 50 of the children (87 percent) tested positive for Covid-19 antibodies—in other words, they had been exposed to the virus; 15 of the kids (26 percent) had an active infection. Other studies have recorded similarly high numbers. Even children who didn’t test positive had a history of being exposed to the virus, says Dr. Mouledoux.

New York State health authorities have already defined MIS-C as a combination of the inflammatory symptoms and exposure to the new coronavirus (known as SARS-CoV-2); doctors are confirming cases of MIS-C in children using these criteria.

The timing of MIS-C has muddied the waters: The cases appear four to five weeks after exposure to the virus. “It seems more like an aftereffect of this infection,” says Dr. Mouledoux. So like Kawasaki disease, MIS-C seems to be preceded by a viral disease, she explains. (Learn more about 11 troubling new symptoms of Covid-19.)

Is MIS-C a faulty immune response?

Given the four-to-five-week time lag, it’s very possible that MIS-C is the product of an abnormal immune-system response—a similar event has happened with many adults, although not with the same symptoms. “It’s an inflammatory immune response and it is probably the body’s way of reacting to the virus,” explains Dr. Mouledoux. “That’s probably why we see it several weeks after the acute phase.”

The main symptom is fever

There’s no diagnostic test for MIS-C, so doctors rely on looking at the constellation of symptoms to put a picture together.

Like Kawasaki disease, a fever seems to be the defining feature of the new syndrome. In the JAMA article, all 58 children had a fever. And in a June 29 study in the New England Journal of Medicine (NEJM), all children with MIS-C reported having a fever and chills.

When they were admitted to the hospital 63 percent had a fever of 100.4°F or higher. The fever had been present for three to 19 days. Fever, of course, seems to be the most common sign of Covid-19 infection.

Abdominal pain and other symptoms

The most common symptom cluster for MIS-C is in the gut—gastrointestinal (GI) distress. “There have been reports of patients presenting with symptoms that are almost like appendicitis,” says Dr. Ergem. “They have inflammation around the intestinal wall and this is quite significant.”

Other GI symptoms have included diarrhea, abdominal pain, nausea, and vomiting, according to the NEJM study. The symptoms are surprising, says Dr. Mouledoux, because the most common serious complications for adults with Covid-19 are respiratory and cardiac.

Other symptoms of MIS-C have included rashes, headache, and sore throat, all of which could easily have many other causes, including other viral infections, she adds. There’s also overlap with Kawasaki symptoms, such as swollen hands and feet and red cracked lips.

Heart complications

MIS-C carries a risk of cardiac problems, ranging from relatively insignificant to heart failure, says Dr. Mouledoux. The most common cardiac complication seen with MIS-C has been inflammation of the heart muscle, or myocarditis. In fact, laboratory tests on these patients have displayed similar results as adults who have had heart attacks but these are not heart attacks, she adds.

Doctors have also seen dilated coronary arteries (which can block blood flow), problems with the heart’s pumping mechanism, irregular heartbeat, and abnormal blood clotting. There have also been reports of aneurysms, says Dr. Ergem. This is one of the most feared complications of Kawasaki disease.

Neurological symptoms

A July report in JAMA Neurology notes neurological symptoms among four out of 27 young patients with MIS-C in London between March 1 and May 8. All had tested positive for the virus that causes Covid-19 either through a nasal swab or an antibody test and all had been previously healthy.

The symptoms included headaches, muscle weakness, and poor reflexes and encephalopathy which the authors attributed to an abnormal immune response. An earlier study of adults with Covid-19 in Wuhan, China found that 36.4 percent had dizziness, headache, and one had seizures. The good news for children is that all four children improved and two recovered completely.

cropped shot of child's hand on hospital bed with IV linesAlexandra Pavlova/Getty Images

How is MIS-C treated?

Doctors are treating children with MIS-C much the same way they have treated KD patients, says Dr. Kim. That means aspirin and intravenous immunoglobulin (antibodies), and, sometimes, steroids.

So far, patients seem to respond to treatment, although some became very sick before getting better. In the NEJM study, 80 percent were admitted to the ICU; two died. “At this juncture, the numbers are small and experiences are limited so we have to be careful about prognosis or outcomes, but based on the experiences we have had so far throughout the world, it appears that most children will recover,” says Dr. Kim. “The fatality is very small, though we will require more information down the line.”

“It’s still a rare occurrence and the majority of these kids do very well,” adds Dr. Ergem. “It’s not like every child who gets Covid-19 will end up getting MIS-C.”

Preventing Covid-19

Nationwide Children’s Hospital advises seeing a doctor if a child has a continuing fever of more than 101°F along with severe abdominal pain, diarrhea, or a rash with no other obvious cause.

Of course, the best “treatment” for Covid-19 is actually prevention. The virus that causes Covid-19 spreads mainly through respiratory droplets between people who are near each other. So, wear a mask, wear a mask, wear a mask.  This is especially important given the growing recognition of asymptomatic transmission. A new study from Ochsner Clinic found that fully 75 percent of people had no symptoms during the early stages of the virus. (Get your child one of these recommended face masks for back-to-school safety.)

Other precautions everyone should be taking include washing your hands often (with soap and water if possible, otherwise an alcohol-based hand sanitizer), not touching your face, staying six feet away from others, and avoiding crowds.

Popular Videos


Amanda Gardner
Amanda Gardner is a freelance health reporter whose stories have appeared in,,, WebMD, HealthDay, Self Magazine, the New York Daily News, Teachers & Writers Magazine, the Foreign Service Journal, AmeriQuests (Vanderbilt University) and others. In 2009, she served as writer-in-residence at the University of Wisconsin School of Medicine and Public Health. She is also a community artist and recipient or partner in five National Endowment for the Arts grants.