Now, researchers from Children's Hospital of Philadelphia (CHOP) report important data that differentiate MIS-C from severe COVID-19 in children and suggest that MIS-C is a post-infectious syndrome related to COVID-19 but distinct from KD. The findings were published in The Journal of Clinical Investigation.

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In the early days of the COVID-19 pandemic, the SARS-CoV-2 virus seemed only rarely to have serious complications in children. However, by April 2020, pediatricians had begun recognizing a syndrome in children who tested positive for COVID-19 involving hyperinflammation and some other attributes found in Kawasaki disease (KD). By May, the Centers for Disease Control and Prevention (CDC) had named the new condition Multisystem Inflammatory Syndrome in Children (MIS-C). Yet the biology of MIS-C and how it relates to or differs from severe COVID-19 in children has largely remained a mystery.

"This is the first report comparing, head-to-head, the distinct outcomes of SARS-CoV2 in children and provides novel information on disease biology, as well as clinical information that can help practitioners distinguish between the clinical syndromes," said Edward M. Behrens, MD, Chief of the Division of Rheumatology at CHOP, member of the Immune Dysregulation Frontier Program, and co-senior author of the paper. "The clinical and laboratory measures we describe accurately distinguish between patients with MIS-C and severe COVID-19, which will help physicians provide better, more accurate treatment for their patients."