Children with a rare but potentially dangerous complication thought to be linked to the coronavirus have now been identified in at least seven states and the Washington, D.C., area.
Doctors say the increase does not necessarily suggest that the number of such cases has grown. Instead, they say, it is likely the result of increased awareness of the problem, which just this week got an official name: pediatric multisystem inflammatory syndrome.
NBC News has found at least 85 such cases in children across the U.S. The majority — 64 — are in New York state, which has also recorded the highest number of COVID-19 cases overall.
Other cases include four patients at Boston Children's Hospital, an estimated five to 10 at Children's Hospital of Philadelphia, three at Children's Hospital Los Angeles, three at Nemours Children's Health System in Delaware, three at Ochsner Medical Center in Louisiana and one at Seattle Children's Hospital.
Children's National Hospital in Washington, D.C., has also reported two patients, but it has 15 more children in intensive care with some kind of massive inflammatory response to COVID-19. It's unclear whether all of those patients indeed have pediatric multisystem inflammatory syndrome.
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"All the kids have some sort of severe inflammation," said Dr. Michael Bell, head of critical care medicine at Children's National Hospital. "I think it's all part of some spectrum of disease that's evolving as we learn more and more about this infection and its consequences."
The newly identified syndrome appears to be the result of a child's immune system going into overdrive after a COVID-19 infection. However, it's still too soon to pin all of the cases on the coronavirus. Some patients have tested negative.
"We're all still waiting for the smoking gun to be sure it is associated with COVID-19," said Dr. Audrey John, chief of pediatric infectious diseases at Children's Hospital of Philadelphia, adding that it's "certainly suspicious."
Pediatric multisystem inflammatory syndrome can mirror symptoms of other inflammatory illnesses, such as Kawasaki disease and toxic shock-like syndrome.
Children can have high fevers, severe diarrhea, rash and often red eyes or conjunctivitis. But "the feature that's been most concerning is that they have problems with their heart function," John said.
"The heart isn't squeezing as well as it should, so they need medications to help keep their blood pressure up," John said.
Children with the condition are also usually treated with intravenous immunoglobulin, an antibody-rich plasma infusion that's been used to treat Kawasaki disease for decades.
Doctors say the young patients will need to be followed closely in the coming years for further heart problems.
Kawasaki disease "puts kids at risk for having coronary problems later in childhood, which can cause premature heart attacks," Bell said. "We have seen patients with COVID-related disease that looked [like] Kawasaki have these coronary artery abnormalities."
No deaths have been reported in the U.S.; however, a 14-year-old boy in the U.K. died. His and other such cases in Europe are detailed in a report published in The Lancet.
Still, COVID-19 complications, which include the possibly-linked new syndrome, are rare in children.
"We want to reassure parents this appears to be uncommon. While Kawasaki disease can damage the heart or blood vessels, the heart problems usually go away in five or six weeks, and most children fully recover," Dr. Jane Newburger, director of the Kawasaki Program at Boston Children's Hospital, wrote in a news release on behalf of the American Heart Association.
John said: "In general, families do not need to worry about this. I doubt that this is really new. I think it's just really newly recognized.
"I hope what comes of this is that, because we're seeing more cases, it will not take long before we will be better at recognizing this and treating it."