Children across the U.S. and Europe are coming down with a rare but life-threatening condition that appears to be connected to covid-19. But as doctors continue to study the ailment, some experts are arguing that it should stop being compared to another rare disorder in children, called Kawasaki disease. Rather, it seems to be its own distinct illness triggered by the novel coronavirus.
Last month, pediatricians in the UK began reporting an apparent surge of peculiar cases: Children with long-lasting fevers, rashes, and other symptoms of widespread inflammation, like reddened eyes. Some children would go on to experience a sudden, dangerous drop in blood pressure, commonly known as shock, that could deprive their organs of oxygen and necessitate intensive care. Many of these children were eventually tested for the coronavirus, either through a PCR test that confirms an active infection or through blood tests that look for antibodies to the virus, and often ended up testing positive.
On the surface, the condition bore a close resemblance to two well-known but rare conditions in children: Kawasaki disease and toxic shock syndrome. So when doctors and organizations initially sounded the alarm for other doctors to look out for these symptoms, they frequently alluded to both conditions, particularly Kawasaki. More cases have now been reported in the U.S., with at least 102 cases being investigated by health officials in New York as of May 13. Kawasaki disease continues to be referenced by health officials and media outlets in talking about the condition, but experts Gizmodo has spoken to say that’s no longer a helpful way of looking at it.
“Pediatricians are trained to think about Kawasaki disease when you see fever, red eyes, red lips, and rash in children,” Stanford Shulman, a pediatric infectious disease specialist at Northwestern University in Chicago, told Gizmodo. “But as our experience has grown, we’re finding that a lot of features in these children are quite unlike most Kawasaki disease patients.”
One of the most glaring differences is age. While Kawasaki predominantly affects children under 5 years old, the age range of victims of this syndrome extends to as far as 21. Another difference is that many children also have stomach pain and other gastrointestinal problems, uncommon symptoms with typical Kawasaki.
Some children with Kawasaki can develop shock and need intensive care, much as these children have—a presentation occasionally referred to by doctors as “kawashocki.” But according to Moshe Arditi, director of the Pediatric Infectious Diseases and Immunology Division at Cedars-Sinai in California, there are still apparent distinctions between those two conditions.
For one, only about 5 percent of Kawasaki patients ever develop shock and need intensive care, while a much higher percentage of these new cases have ended up in the ICU, according to early reports. In addition to the different symptoms, children with the new syndrome also have lab readings that are easily distinguishable from those with typical Kawasaki, such as lower levels of certain white blood cells and platelets.
“These patients shouldn’t be called Kawasaki disease,” Arditi told Gizmodo.
Both Arditi and Shulman agree that the illness has a lot more in common with toxic shock syndrome, particularly when looking at patients’ blood work. But there are some things that don’t quite fit there, either. Toxic shock is most commonly caused by infections from certain kinds of staph and strep bacteria, not viruses. These infections pump out “superantigens” that drive the immune system into a self-destructive frenzy that systemically attacks the body. In the new cases, however, those bacteria have been ruled out as possible causes.
Staph and strep infections in people don’t make superantigens every chance they get, though. Toxic shock usually happens under complicated circumstances, such as an overgrowth of bacteria caused by tampons that are used too long. It’s known that the structure of some viruses make them theoretically capable of producing superantigens. Arditi and his team are now studying whether the coronavirus behind covid-19 could be one of those viruses.
Another possible risk factor for the syndrome, and an argument against it being similar to Kawasaki, is genetics. Kawasaki tends to be more common in children of Asian descent, but doctors in Japan or China haven’t reported any similar spike in Kawasaki-like cases yet, as far as Arditi knows, despite being some of the first places to face covid-19. Different genetic variations may underline a child’s vulnerability to this new syndrome, Arditi said, though more research will be needed to suss that out (other factors, like distinct viral strains in different parts of the world, could be another possible explanation, he added).
At the end of the day, all of these illness classifications are broadly describing a similar dysfunction: a massive overreaction by the immune system that turns against the body. What’s different is the journey getting there and the parts of the body that are involved.
It may turn out that this new syndrome happens in a very similar way as classic toxic shock does or that it’s happening in some other way not yet fully understood. We already know, for instance, that some adults with covid-19 can also develop overactive immune responses, and it’s possible that these complications could be connected to what we’re seeing in kids, Shulman said.
An international group of pediatric specialists have created a diagnostic criteria for the condition and are calling it “pediatric multi-system inflammatory syndrome potentially associated with COVID-19,” or PMIS for short, a term that health officials in New York have adopted. Others have coined the term “covid-19 associated hyperinflammatory syndrome.” Whatever the name, the prognosis is fortunately good for children who become sick.
Though at least three children in New York City have reportedly died from the condition, most have recovered. The standard immune-dampening and anti-inflammatory drugs used to treat cases of Kawasaki or toxic shock also seem to help with these cases, especially if caught early. Overall, the risk of serious illness for children with covid-19 remains much lower than for adults.
On the other hand, these cases are only the latest example of how much more there is to know about the new coronavirus and its effects on the body. That same air of mystery surrounds Kawasaki disease. Despite having been discovered by Japanese pediatrician Tomisaku Kawasaki over 50 years ago, doctors still know very little about it. Covid-19 may lead to a much greater awareness of Kawasaki, according to Arditi.
“One of the few good things that this pandemic has done is what we as Kawasaki disease doctors and researchers couldn’t do in 40, 50 years—within the last two weeks, the whole world has learned about Kawasaki, even if it’s a misnomer for what’s happening,” he said.