MIS-C is more common and more serious than previously reported, study finds

CNN
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Although still rare, post-Covid-19 MIS-C is more common and more severe than previously reported, and there are significant racial disparities in cases, according to study published Thursday in JAMA Network Open.

Multisystem inflammatory syndrome in children – which primarily occurs after infection with Covid-19 – causes inflammation in different parts of the body and can affect major organs, including the kidneys, brain, lungs and heart. It can be serious or fatal.

The US Centers for Disease Control and Prevention currently relies on voluntary case reports from local health departments for MIS-C surveillance. Through November, they applied a total of about 9,000 cases and 74 deaths from MIS-C out of millions of Covid-19 cases among children.

A formal diagnosis code was established for MIS-C in 2021, and the new study analyzed records collected by the Agency for Healthcare Research and Quality from thousands of hospitals representing more than three-quarters of the US population.

It was determined that for every 100 children hospitalized with Covid-19 in 2021, there were about 17 MIS-C hospitalizations. Hospitalizations with MIS-C were typically younger and more likely to occur in male children than hospitalizations due to Covid-19.

The more organs affected, the worse the outcomes. As the number of affected organ systems increased from two to six or more, mortality increased from 1% to 6%, according to the new study. Length of hospital stay doubled from four to eight days, and adverse drug reactions more than tripled from 5% to 18%.

Overall, more than 60% of children hospitalized with MIS-C had more than two organ systems affected. Of these, about 8% of patients had at least six organ systems affected.

Racial disparities in Covid-19 outcomes are well established, and this new research found even greater disparities in MIS-C outcomes.

MIS-C hospitalization was twice as high among black children as among white children. And while black children represented about 24% of all MIS-C cases, they represented 32% of the most severe cases involving at least six organ systems.

The researchers also found that “the severity of MIS-Ca for black children is likely exacerbated by socioeconomic factors,” with those living in the most socially disadvantaged communities typically spending an extra day in the hospital. They did not find the same link with hospitalizations for Covid-19.

These findings “increase our knowledge of the differences and outcomes of MIS-C and COVID-19, elucidating the risks and impacts of increasing organ system dysfunction,” according to a study commentary by pediatricians and researchers from the University of Colorado School of Medicine.

But they raise even more critical questions, including the specific reasons for the vast racial disparities.