Multisystem inflammatory syndrome in children rose and fell with the first wave of the COVID-19 pandemic in France.

Aim: This study determined the influence of the COVID-19 pandemic on the occurrence of multisystem inflammatory syndrome in children (MIS-C) and compared the main characteristics of MIS-C and Kawasaki disease (KD).

Methods: We included patients aged up to 18 years of age who were diagnosed with MIS-C or KD in a paediatric university hospital in Paris from 1 January 2018 to 15 July 2020. Clinical, laboratory and imaging characteristics were compared, and new French COVID-19 cases were correlated with MIS-C cases in our hospital.

Results: There were seven children with MIS-C, from 6 months to 12 years of age, who were all positive for the virus that causes COVID-19, and 40 virus-negative children with KD. Their respective characteristics were as follows: under 5 years of age (14.3% vs. 85.0%), paediatric intensive care unit admission (100% vs. 10.0%), abdominal pain (71.4% vs. 12.5%), myocardial dysfunction (85.7% vs. 5.0%), shock syndrome (85.7% vs. 2.5%) and mean and standard deviation C-reactive protein (339 ± 131 vs. 153 ± 87). There was a strong lagged correlation between the rise and fall in MIS-C patients and COVID-19 cases.

Conclusion: The rise and fall of COVID-19 first wave mirrored the MIS-C cases. There were important differences between MIS-C and KD.