Clues to Rare Disorder Affecting Kids With COVID-19

TUESDAY, May 18, 2021 (HealthDay News) -- New insight into a rare and dangerous disorder that can occur in kids with COVID-19 could improve treatment of the condition, researchers say.

Many children infected with SARS-CoV-2 (the virus that causes COVID-19) go undiagnosed or have no symptoms, but about one in 1,000 develop a condition called multisystem inflammatory syndrome in children (MIS-C) within four to six weeks.

Symptoms include fever, abdominal pain with vomiting and/or diarrhea, rash, and heart and nervous system problems.

With early diagnosis, MIS-C is treatable with immune suppressants such as steroids. Left untreated, it can be fatal.

"Why does this happen when there is no virus or antiviral response still present in kids? And why is it only occurring in youth?" said study co-author Carrie Lucas, an assistant professor of immunobiology at Yale University in New Haven, Conn.

To find answers, she and her colleagues tested blood from kids with MIS-C, adults with severe COVID-19 symptoms, as well as from healthy kids and adults.

The kids with MIS-C had immune system signatures distinct from the other groups, the researchers discovered.

Specifically, they had high levels of alarmins — molecules that are part of the innate immune system that quickly responds to all infections.

Previous research has suggested that a child's innate immune system response may be stronger than adults', and that could be one reason why they typically have milder symptoms after infection with the new coronavirus.

"Innate immunity may be more active in children who are infected with virus," Lucas said in a university news release. "But on the flip side, in rare cases it may get too revved up and contribute to this inflammatory disease."

The investigators also found that kids with MIS-C had a marked elevation of certain adaptive immune responses. These are defenses that typically prompt the body to remember and respond to specific pathogens (such as viruses, bacteria, fungi or parasites).

But instead of being protective, the researchers explained that the responses in kids with MIS-C appear to attack a variety of host tissues — a hallmark of autoimmune diseases.

The initial immune response in these cases triggers a cascade that damages healthy tissue, which in turn makes it more susceptible to attack by autoantibodies, Lucas suggested. An autoantibody is one produced by the immune system that mistakenly reacts with a person's own organs or tissues.

Knowing the particular immune system signatures of MIS-C could help in the diagnosis and early treatment options of children at high risk for the disorder, Lucas said.

The findings were published recently in the journal Immunity.

More information

The U.S. Centers for Disease Control and Prevention has more on MIS-C.

SOURCE: Yale University, news release, May 14, 2021