Incidence Trends, Outcomes, and Factors Associated with Mortality in Multisystem Inflammatory Syndrome in Children: A Nationwide Study in Thailand during 2021-2023

OBJECTIVES: Multisystem inflammatory syndrome in children (MIS-C) is a severe post-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inflammatory condition. This study described MIS-C epidemiology and outcomes in Thailand during 2021-2023 and identified predictors of in-hospital death. METHODS: A nationwide retrospective cohort study used Thai National Health Security Office (NHSO) inpatient data. Children aged 1 month to <18 years with MIS-C (ICD-10-TM codes U10 and U10.9) were included. Severe manifestations, organ dysfunction, and procedures were identified using ICD-10-TM, and ICD-9-CM codes. Logistic regression was used to evaluate mortality predictors. RESULTS: Among 634 MIS-C hospitalizations (59.2% male; median age 6 years), National incidence peaked at 3.2 per 100,000 in 2022. In-hospital mortality was 3.2% with regional heterogeneity. Severe cardiac manifestations occurred in 37.4% and severe respiratory manifestations in 12.0%. Malignancy (adjusted odds ratio [AOR] 17.13; 95% confidence interval [95% CI] 1.84-159.92) and disseminated intravascular coagulation (DIC) (AOR 14.16; 95% CI 2.10-95.37) independently predicted mortality. CONCLUSIONS: MIS-C burden peaked in 2022 with regional variation. Early risk stratification and timely critical care with advanced organ support remains essential to optimize survival.