Children older than 5 at higher risk of COVID-19-related multisystem inflammatory syndrome

The international study included 232 children younger than 18 admitted to 1 of 15 centres-13 in Canada, 1 in Costa Rica and 1 in Iran-for suspected MIS-C between March 1, 2020, and March 7, 2021. The patients met the World Health Organization's definition for MIS-C, which includes fever persisting for at least 3 days; elevated C-reactive protein, which indicates inflammation; illness involving 2 or more systems with no obvious microbial cause of inflammation; and positivity for COVID-19 or suspected contact with a positive case.

Most patients (89%) had gastrointestinal symptoms such as pain and dermatological problems like rashes and swelling (85%). Cardiac involvement was common (59%), as were abnormalities in blood coagulation (90%). Of the 232 children, 73 (31.5%) were admitted to ICU, and 47 (64%) of them needed treatment for very low blood pressure.

The risk of admission to the ICU was higher in children aged 6-12 years (44%) and 13-17 years (46%) than in children aged 0–5 years (18%). As well, children admitted to hospital later in the pandemic (between November 2020 and March 2021) were more likely to be admitted to the ICU (50 of 112, 45%) than those hospitalized earlier (23 of 120, 19%).

The authors note challenges in diagnosing MIS-C.

"Multisystem inflammatory syndrome in children is a new diagnosis, with differing diagnostic criteria that have not been validated," writes Dr. Joan Robinson, a pediatrician at the University of Alberta, Edmonton, Alberta, with coauthors.

"Most of these children lacked a history of contact with a person with proven SARS-CoV-2 infection. Identifying exposure can be difficult as infected contacts may be asymptomatic or may never have been tested."

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10.1503/cmaj.21087