Multisystem inflammatory syndrome in children related to COVID-19: A systematic review
Authors: Hoste Levi , Van Paemel Ruben , Haerynck Filomeen 
Published: August 2020

AbstractImportanceIn April 2020, multiple reports of an association between a hyperinflammatory, Kawasaki-like condition and SARS-CoV-2 were published and termed as pediatric inflammatory multisystem syndrome (PIMS) or multisystem inflammatory syndrome (MIS). A thorough characterization of this syndrome (demographics, presentation, diagnosis, and outcome) is currently lacking.ObjectiveWe aimed to perform a systematic review of published cases of this novel multisystem inflammatory syndrome in children associated with COVID-19.Evidence reviewA literature search of Pubmed, Embase, BioRxiv, MedRxiv and COVID-19 specific research repositories (Cochrane COVID-19 Study Register and the World Health Organization (WHO) COVID-19 Global Research Database) was conducted from December 30th, 2019 to June 30th, 2020. Publications describing inflammatory syndromes associated with COVID-19 were included. Of 333 unique publications, 229 records were excluded based on title and abstract. After screening the full text, 40 observational studies and case reports were included, comprising 687 cases (published between May 9th, 2020 and June 30th, 2020).FindingsIn contrast to classic Kawasaki disease, epidemiological enrichment for adolescents (median age 9 [6.0-12.3]) and ethnic minorities (35.8% black and 24.5% Hispanic/Latino) was observed. There was a male predominance (59.1%). Apart from obesity (24.4%), pre-existing conditions were infrequent. The majority suffered from gastrointestinal (87.2%) and cardiocirculatory (79.2%) manifestations. Respiratory symptoms (51.2%) were less frequent. Over half of patients (56.3%) presented with hemodynamic shock, and critical care interventions were often necessary (inotropics (56.5%), mechanical ventilation (22.9%), non-invasive ventilation (30.6%), extracorporal membrane oxygenation (ECMO;4.5%)). Anti-SARS-CoV-2 IgG and RT-PCR were positive in respectively 69.4% and 36.7%. Eleven deaths were reported (1.6%). The RCPCH case definition proved to be most comprehensive comprising all single cases. In contrast, WHO and CDC MIS definitions are more stringent, with the CDC case definition often missing severe cases requiring intensive care (n = 33 out of 95 cases).Conclusions and RelevanceThis novel pediatric multisystem hyperinflammatory condition, associated with COVID-19, is characterized by a severe and heterogeneous disease spectrum. Despite frequent intensive care interventions, mortality rate was low and short-term outcome favorable. Long-term follow-up of possible chronic complications and additional clinical research, to elucidate the underlying immunological pathogenesis and possible genetic predisposition is crucial.Key pointsQuestionHow is the novel pediatric multisystem inflammatory condition associated with coronavirus disease 2019 (COVID-19) characterized?FindingsThis systematic review of 40 studies, comprising 687 cases, represents the heterogeneous spectrum of this novel pediatric disease related to COVID-19, including contrasting features with previously-described hyperinflammatory conditions. Adolescents and particular racial/ethnic minorities are affected more. Gastrointestinal and cardiocirculatory manifestations are often found, along with critical care interventions. Nevertheless, only 11 deaths are reported.MeaningThis novel condition has variable severity but good short-term outcome. Uniform case definitions are required to guide future (preferably controlled) research on epidemiological clustering, immunopathology, and long-term prognosis.