After contracting and beating a coronavirus infection, a body needs time to rest, to recover its health and strength. Sadly, for some children, that isn't what happens next.
A mysterious, new disease called multisystem inflammatory syndrome in children (MIS-C, and also known as paediatric multisystem inflammatory syndrome or PIMS) has affected hundreds of children around the world since it was first discovered earlier this year.
The condition, thought to be somehow linked to COVID-19, can emerge in kids even after very mild coronavirus infections. But a light case of coronavirus is no guarantee that a subsequent case of MIS-C won't be very serious, and sometimes even fatal.
"Children did not need to exhibit the classic upper respiratory symptoms of COVID-19 to develop MIS-C, which is frightening," says neonatologist Alvaro Moreira from the University of Texas Health Science Centre at San Antonio.
"Children might have no symptoms, no one knew they had the disease, and a few weeks later, they may develop this exaggerated inflammation in the body."
In a comprehensive new review of medical research into MIS-C, all of it from this year, Moreira and his team uncovered almost 40 observational studies involving 662 child patients in total who developed the syndrome.
MIS-C is marked by severe inflammation in multiple parts of the body, including, the heart, lungs, kidneys, brain, skin, eyes, and more. The symptoms resemble two other conditions – Kawasaki disease and toxic shock syndrome – but the amount and spread of overall inflammation in MIS-C is worse, Moreira says.
"It can be lethal because it affects multiple organ systems," Moreira says. "Whether it be the heart and the lungs, the gastrointestinal system or the neurologic system, it has so many different faces that initially it was challenging for clinicians to understand."
Now, several months into the COVID-19 pandemic, we're getting a clearer picture of what MIS-C looks like, although there's still much we don't understand about the syndrome – as well as what the long-term recovery prospects will be for the young people who experience this severe condition.
Of the 662 known cases worldwide looked at in the new review, 71 percent of the children were admitted to intensive care, and the average length of hospital stay was about eight days.
In every case, the patients showed fever, and the majority also presented with abdominal pain or diarrhoea (73.7 percent of cases) and vomiting (68.3 percent). Conjunctivitis and rash was also common.
Sadly, 11 of the children in the studies died. While this observed death rate for children with MIS-C does appear to be low (at about 1.7 percent of all child patients in this study), the researchers point out that this figure is actually much higher than the 0.09 percent mortality rate observed in children with COVID-19.
In cases where children did recover, however, there's a lot of concern about what MIS-C might be doing to their hearts. In the study, about 90 percent of the children had an echocardiogram (EKG) test, and more than half (54 percent) of the results that came back showed abnormalities.
These abnormalities included dilation of coronary blood vessels, depressed ejection fraction (reduced ability for the heart to pump oxygenated blood to body tissues), and in about 10 percent of patients, an aneurysm of a coronary vessel, which could put them at higher risk of future cardiac events.
"These are children who are going to require significant observation and follow-up with multiple ultrasounds to see if this is going to resolve or if this is something they will have for the rest of their lives," Moreira says.
"That's catastrophic to a parent who had a previously healthy child and then he/she is in the very small percentage of individuals who developed MIS-C after COVID-19 infection."
The authors note a number of limitations to their study, and point out that they may have missed some studies of MIS-C despite their wide search.
Nonetheless, while there's still a lot we don't know about MIS-C, the picture that's starting to emerge is something we have to take very seriously: a disease associated with COVID-19 that for many children who experience it is much worse than the COVID-19 they've already encountered.
In the rare cases where MIS-C is suspected, early medical attention is a crucial action that can save children's lives.
"Children will typically show signs/symptoms of MIS-C three to four weeks after COVID-19 infection and many will progress rapidly into shock and cardiorespiratory failure," the authors write in their study.
"Families should seek immediate medical care as children with this condition decompensate quickly and most children will need management in an intensive care unit. Overall, children will survive this hyperinflammatory condition with administration of IVIG, steroids, a multidisciplinary team of healthcare providers, and in some cases immunomodulatory agents."
The findings are reported in EClinicalMedicine.