Other reports rolled in – a death in France, a cluster in Italy – and in the US, the CDC put together what was observed of the unusual condition and asked doctors to report cases that were consistent with departments of state health. Coming up with a definition of the case is a first step in conducting oversight for what a new illness may be. In mid-May, the CDC learned from more than 100 American children with the condition, three of whom had died.
On August 7, the agency updated those figures. As of the end of July, 570 American children had experienced constellation of shock, heart problems, and gastrointestinal problems; had blood work that indicated that inflammation was continuing in their bodies; and were positive for Covid-19. Many of them were seriously ill: 364 had to be treated in an ICU, and 10 died. In many of them, various organs – heart, lungs, kidneys and brain – were affected, which deserves the attention given to the agreed new “multi-system inflammatory syndrome in children” name. Almost one in five of the survivors was left with kidney damage as well as with weakened arteries and aneurysms, for which they require long-term treatment and control of medication.
Many of those cases came through a research network overseen by Randolph, the Overcoming Covid project, which collects case reports from 70 pediatric referral hospitals in the U.S. and collects blood and respiratory samples from patients to prepare for clinical trials in children with acute Covid-19 and with MIS-C. The network published its first record in June, discovering 186 child and teen patients in 26 states and confirming the new syndrome was “serious and life-threatening disease”, including four deaths. “I think people are very aware of this now,” Randolph says. “They also recognize less severe cases and determine that there is a spectrum of disease.”
It seems clear at this point that MIS-C is not Kawasaki: The children affected by the new syndrome are schoolchildren and teenagers, while Kawasaki is most common in toddlers. And almost every child reported with MIS-C shows evidence that they had a new infection with coronavirus, while the underlying cause of Kawasaki is not known. But the similarities between the two are enough to illuminate the science of both.
‘If you ask the question’ Are these two diseases the same? ‘The answer is clearly not,’ says Jane Burns, a professor of pediatrics and director of the Kawasaki Disease Research Center at the University of California, San Diego. “If you mean by the same thing, ‘Are these immunological responses in specifically genetically susceptible children, did that happen as a result of an exposure that these children had, and then do they give an unusual immune response to that exposure?’ Then yes, they are exactly the same. “
This can be a critical insight, as it is actually not uncommon for children to have inflammatory responses to an infection, and for doctors to never find out what the cause was. However, it may take some time for researchers to gather enough data to understand the immune processes that trigger MIS-C, even with the help of networks like Randolph’s.
“Learning what a genetic predisposition might be requires tons of samples because it’s probably not due to one rare mutation,” says Burns, who has seen 10 MIS-C patients at her center. As with Kawasaki disease, she said, “it’s probably a complex path” that allows for a range of answers, from very mild disease to the most serious versions that children place in ICUs.
Finding a genetic link will be challenging, as MIS-C is simply rare given the numbers found, occurring in only about two children out of 100,000. However, researchers are concerned that it is not as unusual as those numbers may seem, because the definition of the MIS-C case in which a child is counted requires evidence of infection as exposure – and like many times has been observed since the start of the pandemic, children can carry the virus without symptoms so that their cases are not consistently recognized or recorded.
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