SARS-CoV-2-associated infection (COVID-19) initial reports indicated a relative sparing of children inversely related to their age during the pandemic. Children and neonates showed a decreased incidence of SARS-CoV-2 infection and, if infected, manifested a less severe phenotype, partly because of an enhanced innate immune response. 

However, a multisystem inflammatory syndrome in children (MIS-C) or pediatric inflammatory, multisystem syndrome temporally associated with SARS-CoV-2 was reported that involved coronary artery aneurysms, cardiac dysfunction, and multiorgan inflammatory manifestations. MIS-C shows similarities to Kawasaki disease and other inflammatory conditions and may fit within a spectrum of inflammatory conditions based on immunological results. 

More recently, neonates born to mothers with SARS-CoV-2 infection during pregnancy showed evidence of a multisystem inflammatory syndrome with raised inflammatory markers and multiorgan, particularly cardiac dysfunction that has been described as a multisystem inflammatory syndrome in neonates (MIS-N). Yet, there exists a variation in definitions and management algorithms for MIS-C and MIS-N. Understanding baseline immunological responses will aid prognostication and inform optimal immunomodulatory therapies by stratifying patient groups and identifying accurate diagnoses.

Molloy EJ, Nakra N, Gale C., et al. Multisystem inflammatory syndrome in children (MIS-C) and neonates (MIS-N) associated with COVID-19: optimizing definition and management. Pediatr Res. 2022. https://doi.org/10.1038/s41390-022-02263-w