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.