COVID-19 was thought largely to spare children. That may no longer be the case

Boston Children's Hospital, seen from the Fazzalari Sky Bridge over Longwood Avenue.Lane Turner/Globe Staff

A rare and mysterious inflammatory syndrome afflicting as many as 100 children in New York has emerged in Massachusetts, upending prevailing notions about COVID-19′s impact on the young, who were initially thought to be largely spared of serious illness from the coronavirus outbreak.

Boston Children’s Hospital has treated six patients with what doctors are now calling “pediatric multi-system inflammatory syndrome,” which may be linked to the coronavirus. The new syndrome affects multiple organs, and its symptoms include fever, skin rashes, and eye redness. Two of the children are currently hospitalized at Boston Children’s, though not in the intensive care unit, according to a spokeswoman. MassGeneral Hospital for Children has treated at least four patients with the syndrome, a spokeswoman confirmed. Baystate Children’s Hospital in Springfield also has seen a small but unspecified number of cases of the puzzling new illness, according to Dr. Donna Fisher, the hospital’s chief of infectious diseases.

“Children were thought to be protected from COVID, and there were very few cases of severe complications, and the majority of those cases with severe complications were in children with a lot of underlying conditions that would predispose them to getting sick," said Dr. Adrienne Randolph, a senior critical care physician at Boston Children’s Hospital. “Now we’re seeing this complication in children who are relatively healthy as well.”

This new inflammatory syndrome has mystified physicians since reports of the condition first surfaced in the United Kingdom in April and made headlines in the United States last week. Doctors don’t know why this new syndrome, which resembles a rare childhood inflammatory illness known as Kawasaki disease, has affected some children, including previously healthy ones, or why children are at greater risk of developing this condition than adults.

“The short answer is that we don’t honestly know,” said Dr. Jane Newburger, a cardiologist and director of Boston Children’s Kawasaki Program. “But we think it could be a direct effect of the virus. It could also be, we think, more likely, the body’s own reaction to the virus or even the antibodies the body is making against the virus that is causing this extreme inflammatory reaction.”

Dozens of cases of the new syndrome have been reported across the United States, including in places hard hit by the pandemic, like New York, New Jersey, Connecticut, Michigan, Washington, and Louisiana, in addition to several countries in Europe. In New York, where at least three children linked to the dangerous new disease have died, about 100 cases are under investigation.

Randolph of Boston Children’s is leading a nationwide study, called “Overcoming COVID-19,” on the effect of the virus in children and young adults age 25 and younger, with $2.1 million in funding from the Centers of Disease Control and Prevention. As of Wednesday morning, Randolph said she had collected preliminary reports of suspected cases of pediatric multi-system inflammatory syndrome from hospitals in 19 states and Washington, D.C.

The state’s Department of Public Health is working with hospitals to gather data on the new syndrome, said department spokeswoman Ann Scales, and hopes to release a “complete statewide count soon."

The symptoms of pediatric multi-system inflammatory syndrome are similar to Kawasaki disease, a rare and poorly understood condition that causes inflammation in the blood vessels and, in severe cases, aneurysms in the coronary arteries. Like Kawasaki patients, children with this new inflammatory condition are arriving at hospitals with high fevers, rashes, bloodshot eyes, swollen hands and feet, and in some alarming instances, enlarged coronary arteries.

Many of these patients don’t exhibit the tell-tale respiratory symptoms associated with COVID-19. Several have not tested positive for infection, and only through antibody testing is their exposure to the coronavirus later confirmed.

Unlike Kawasaki disease, which primarily afflicts infants and children younger than 5, several cases of this new condition have occurred in older children and teenagers, Newburger said. Children with this syndrome also tend to be sicker than the typical Kawasaki patient, according to Newburger, with more inflammation and gastrointestinal symptoms, like diarrhea and vomiting. Some patients with this COVID-related disease have shown signs of toxic shock, a rare and life-threatening complication among Kawasaki sufferers, characterized by low blood pressure and an insufficient supply of blood to the body’s organs, Newburger said.

A small study published on May 7 in The Lancet of eight children with the new syndrome may provide some clues about the condition’s etiology: All except one of the children were “well above the 75th percentile for weight,” according to the paper, and six were of Afro-Caribbean descent. It’s unknown whether those children were disproportionately represented based on socioeconomic or biologic factors, Newburger said.

“That’s kind of the million dollar question," she said. “Is this overrepresentation related to the fact that there are social factors that cause them to be more likely exposed, or is it something fundamental?”

Doctors are treating the new disease with therapies that have been effective in Kawasaki patients, including intravenous immunoglobulin, anticoagulation medications, and steroids for curbing inflammation, Newburger said. Some children have needed respiratory support.

At Yale New Haven Children’s Hospital in Connecticut, three children have been treated for the new syndrome. Dr. Thomas Murray, a pediatrician at Yale New Haven specializing in infectious diseases, said all three required intensive care at some point during their hospitalization and improved with anti-inflammatory treatment.

While the new syndrome is still relatively rare, Murray said, he wouldn’t be surprised if case numbers continue to rise as public awareness of the condition increases. Parents should alert their family’s pediatrician if their children show any signs associated with the new disease — whether or not they’ve had a known exposure to the coronavirus — including persistent fever, skin rashes, eye redness, abdominal pain, and muscle aches.

“Compared to adults, children have been very, very fortunate. ... Even with this rare complication, the adults have still had to deal with a much higher burden of disease than children," Murray said. "Having said that, this has the potential, when it does occur, to be a very serious complication. The good news is we can treat it, but ... it’s definitely something new and different that up until a few weeks ago we certainly weren’t expecting.”