Examining the time and place of MIS-C cases

Although multisystem inflammatory syndrome in children (MIS-C) has been a cause for concern, important pieces of information such as clinical characteristics and geographic distribution have not been completely studied. An investigation in JAMA Pediatrics offers some key insights.¹

The investigators did a cross-sectional analysis on both clinical and laboratory data collected from children who had MIS-C. Children and young adults were included if the illness onset occurred from March 2020 to January 2021 and they met the MIS-C case definition. To assess for temporal trends, investigators divided the children and young adults into illness onset before July 1, 2020, and illness onset after July 1, 2020. The geographic trends were examined by state, the 4 US census regions, and the level of urbanicity. Urbanicity was classified using the National Center for Health Statistics urban-rural classification scheme, which divided counties into 6 categories: (1) large central metro, (2) large fringe metro, (3) medium metro, (4) small metro, (5) micropolitan, and (6) noncore-nonmetropolitan.

There were a total of 1733 patients with MIS-C in the study. More than half were male and the majority (71.3%) were either Hispanic or non-Hispanic Black. Rash, gastrointestinal symptoms, and conjunctival hyperemia were described by 53% (n = 931) to 67% (n = 1153) of the patients. Hypotension or shock occurred in 937 patients and 1009 required an admission to intensive care. A variety of cardiovascular concerns were reported including cardiac dysfunction in 484 patients, pericardial effusion in 365, myocarditis in 300, and coronary artery dilatation or aneurysms in 258. Very young patients, those aged 0 to 4 years, were found to have the lowest proportion of severe manifestations of MIS-C, but 171 did have hypotension or shock and 197 required admittance to intensive care. Those aged 18 to 20 years had the highest proportion of myocarditis (17 [30.9%]), pneumonia (20 [36.4%]), acute respiratory distress syndrome (10 [18.2%]), and polymerase chain reaction positivity (39 [70.9%]). In the cohort, 24 patients died. The 18- to 20-year-old group also had the highest proportion who reported a preceding coronavirus disease 2019 (COVID-19)-like illness (63%). Across the United States, the first 2 peaks of MIS-C came 2 to 5 weeks after the COVID-19 peaks. Cumulative incidence of MIS-C per 100,000 persons aged younger than 21 years was 2.1 and varied by state from 0.2 to 6.3.

The investigators concluded that the temporal link between MIS-C and the COVID-19 pandemic implied that MIS-C resulted from a delayed immunologic response to severe acute respiratory syndrome coronavirus 2 infection. Clinical manifestations of MIS-C were varied and differed by age as well as the presence or absence of a preceding COVID-19 infection.

Reference

1. Belay E, Abrams J, Oster M, et al. Trends in geographic and temporal distribution of US children with multisystem inflammatory syndrome during the COVID-19 pandemic. JAMA Pediatr. April 6, 2021. Epub ahead of print. doi:10.1001/jamapediatrics.2021.0630