Comparison of Multisystem Inflammatory Syndrome in Children (MIS-C) and Kawasaki Disease

In Korea, studies on multisystem inflammatory syndrome in children (MIS-C) are mostly review articles or case reports, and there are limited original articles directly comparing MIS-C and Kawasaki disease (KD). The purpose of this study was to compare the characteristics of MIS-C and KD in Korean children. Medical records of 22 patients hospitalized with MIS-C from January 2020 to December 2022 were retrospectively reviewed. The control group included 140 patients hospitalized with KD before the COVID-19 pandemic. Compared to the KD group (n = 140), the MIS-C group (n = 22) was older and had a longer hospitalization (P < 0.001). All patients in both groups had at least one KD-like features (e.g., rash, conjunctivitis, or mucositis), but complete KD was more common in the KD group than in the MIS-C group (P = 0.020). Laboratory abnormalities, such as elevated C-reactive protein (CRP), were found in both groups, but some laboratory abnormalities, such as thrombocytopenia or hypoalbuminemia, were more common in the MIS-C group (P < 0.001). Multi-organ dysfunction was observed in 100% of the MIS-C group and 13% of the KD group (P < 0.001). The infectious trigger, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in 100% of the MIS-C group, but no pathogen was identified in the KD group (P < 0.001). KD-like features and systemic inflammation (i.e., CRP ≥ 3.0 mg/dL) are shared findings of MIS-C and KD, whereas organ dysfunction and SARS-CoV-2 are distinct findings of MIS-C that distinguish it from KD.