70 - MULTISYSTEM INFLAMMATORY SYNDROME IN CHILDREN ASSOCIATED WITH COVID-19 IN JAPAN: A NATIONWIDE SURVEY

Background: Multisystem inflammatory syndrome in children (MIS-C) is a systemic inflammatory disorder that is linked to an antecedent COVID-19 in children. MIS-C shows some clinical overlap with Kawasaki disease (KD) but has a different epidemiological feature. The clinical characteristics of MIS-C in Japan, where KD is most frequent, are unknown. This study aims to identify the epidemiological/clinical features and short-term outcomes by a newly established nationwide survey in Japan.

Methods: An observational, multicenter registry system was established in August 2020. The targeted population was MIS-C, SARS-CoV-2 positive KD, and moderate to severe COVID-19 in children, from November 2020 to March 2023. Using a case reporting form, 2,080 facilities were targeted for collecting data such as demographics, information for antecedent SARS-CoV-2 infection, clinical symptoms, laboratory and imaging data, treatments, short-term outcomes, and vaccination status. All cases were reviewed centrally to verify their primary diagnosis by the committee consisting of members from the 4 major medical societies associated with MIS-C/KD in Japan. In this study, we described and statistically analyzed the data of MIS-C cases.

Results: 397 patients were registered, including 118 of MIS-C, 66 of SARS-CoV-2 positive KD, and 189 of moderate/severe COVID-19, as a primary diagnosis. A central review finally determined 129 MIS-C patients, with a mean age of 8.8±3.7 years. Eighty percent of the MIS-C patients occurred during the Omicron predominant period. Seventy-one percent of the MIS-C patients met the KD criteria including 61% of complete and 11% of incomplete criteria, more frequent in younger ages (0-4 years, 80%). Cardiovascular (88%) and gastrointestinal (90%) involvement were frequent. MIS-C in Japan showed less severe clinical pictures with shock in 29%, intensive care unit admission in 12%, and use of inotropes in 11%. Coronary artery lesions (CAL) were present in 10 cases (8%), among them 7 (5%) were present CAL at admission, and 7 (5%) remained CAL at discharge. No fatal cases were reported.

Conclusion: This is the first nationwide report for MIS-C in Japan. Although the number of MIS-C cases in Japan was small, their clinical features were distinctive in that they showed a more KD-like phenotype with less severe clinical pictures. The present study could be the future essential source for a deep understanding of the pathophysiology of MIS-C and KD.