In May 2020, doctors announced they were seeing a new and rare coronavirus complication in children. Now, a year later, Yale researchers say they know why it happens.
Called MIS-C, which stands for multisystem inflammatory syndrome in children, the complication manifests roughly four to six weeks after a coronavirus infection. Experts suspect that children who develop this syndrome were exposed to the virus and that their bodies mounted an exaggerated immune response, The Atlanta Journal-Constitution’s Helena Oliviero wrote.
The condition is marked by a variety of symptoms, including fever, abdominal pain with vomiting and/or diarrhea, rash, and cardiovascular and neurological problems, the Yale team wrote. If diagnosed early, the condition is readily treatable with immune suppressants such as steroids. If left untreated, however, it can be fatal.
Early reports compared MIS-C with Kawasaki Disease because of the common presentation with fever, rash and coronary aneurysms. However, the Yale team wrote, “MIS-C predominantly affects older children with an increased prevalence among Black and Hispanic/Latino populations, whereas KD affects very young children with higher occurrence in East Asian populations.”
In their analysis, Carrie Lucas, an assistant professor of immunobiology at Yale and corresponding author of the new study, and her team tested blood from children with MIS-C, adults with severe COVID-19 symptoms, as well as healthy children and adults. They found children with MIS-C had immune system signatures distinct from other groups.
They found the MIS-C kids had high levels of alarmins — molecules that make up part of the innate immune system that is mobilized to respond to infections. Other research findings have suggested that a child’s innate immune system response might be stronger than an adult’s, which is one explanation for why children generally have milder symptoms.
“Innate immunity may be more active in children who are infected with virus,” Lucas said. “But on the flip side, in rare cases it may get too revved up and contribute to this inflammatory disease.”
The MIS-C patients were also found to have an increase of certain adaptive immune responses, which are defenses to combat specific pathogens — such as the virus causing COVID-19 — and that typically confer immunological memory. But instead of being protective, the responses produced in these kids appear to attack a variety of host tissues, a hallmark of autoimmune diseases.
Lucas said the initial immune response in these rare cases triggers an event that damages healthy tissue, which in turn makes the tissue more susceptible to attack by autoantibodies.
In the meantime, Lucas said, her team’s findings could help in the diagnosis and early treatment options of children at high risk of the disorder.
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