Characterization of Multisystem Inflammatory Syndrome in Children (MIS-C) and Its Relationship to Kawasaki Disease

Study Summary

Beginning in mid-March 2020, pediatricians in communities in Western Europe, the UK, and the Eastern U.S. that had been severely affected by the Covid-19 pandemic noted an increased number of children presenting with fever and evidence of severe inflammation who required admission to intensive care. The syndrome was branded by the CDC in the U.S. as Multisystem Inflammatory Syndrome in Children (MIS-C). The most severely affected children presented with heart failure leading to shock and the absence of significant pulmonary disease. The clinical presentation in these patients shared many features with Kawasaki disease (KD), a self-limited pediatric vasculitis that can result in coronary artery aneurysms.The inflammatory markers, however, were much higher even than KD shock syndrome, a variant of KD presenting with distributive shock and requiring inotropic and vasoactive support in the ICU. Some patients were polymerase chain reaction (PCR)+ for SARS-CoV-2 while most were virus-negative but had detectable antibody suggesting that MIS-C was an immune-mediated reaction to antecedent exposure to the virus. While patients were being diagnosed with shock and MIS-C, children with a milder version of MIS-C that shared many features of KD were being diagnosed in these same regions.