Multisystemic inflammatory syndrome in children post-COVID-19: clinical-biological characteristics of patients in the first year of the pandemic

Introduction: Initially considered the “hidden victims” of the pandemic, children have come into the spotlight regarding the impact of COVID-19 since spring 2020. Against this background, a new entity of multisystemic hyperinflammatory syndrome in the pediatric population with manifestations that overlap with Kawasaki disease has become an increasing focus of attention. Objectives: The current study was intended to identify some indicators of the severity of pediatric inflammatory multisystem syndrome, temporally associated with SARS-CoV-2/multisystemic inflammatory syndrome in children post-COVID-19 (PIMS-C/MIS-C) and factors predictive of its prognosis, paying attention to both already established factors (cardiac injury markers) and less used parameters (neutrophil-to-lymphocyte ratio [NLR], platelet-to-lymphocyte ratio [PLR]) that could provide valuable information for predicting severe disease development. Materials and methods: This study was based on a descriptive observational analysis of a group of pediatric patients (0-18 years) in whom the following were identified: persistent fever, the presence of single/multiple-organ dysfunction, a significant biological inflammatory syndrome, a temporal association with SARS-CoV-2 infection (infection/exposure 2-6 weeks previously), and an absence of other conditions that could explain this pattern. Results: The patients who met the criteria for inclusion in the study during the analyzed period were children aged between 4 months and 17 years and 10 months, with a median age of 5 years (IQR, 3-8.75). All enrolled patients presented fever (with a maximum duration of 9 days) at admission, which was associated at varying rates with digestive, neurological, and skin-mucosal changes, and cardiac manifestations. Three main phenotypes of the condition were outlined (Kawasaki-like, shock-like, and a non-specific form). In the evaluated patients classified into the Kawasaki-like phenotype, higher median values of NLR but lower values of PLR were observed compared with those in the other forms of PIMS-C/MIS-C. Conclusions: The current study outlines the spectrum of PIMS-C/MIS-C while also emphasizing the importance of establishing certain correlations between biological markers and the evolution of the disease. The use of certain parameters easily obtained from the blood count (NLR, PLR) as well as determining their correlation with disease severity could offer new directions to treat this condition