Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) causes an acute respiratory illness (COVID-19). Most children with COVID-19 recover fully; however, some exhibit multisystem inflammatory syndrome in children (MIS-C), a hyperinflammatory disorder affecting multiple organs that generally occurs 2–6 weeks after the onset of COVID-19 [1]. In patients with MIS-C, cardiovascular manifestations, including myocardial dysfunction and coronary artery lesions, are common, and intensive care is occasionally required for cardiogenic shock [[2], [3], [4]].

During the COVID-19 pandemic, cases of Kawasaki disease (KD) were reported in patients with COVID-19. This disease is a self-limiting systemic vasculitis of unknown origin, occurring several weeks after the onset of COVID-19 [5,6]. The clinical features of MIS-C overlap with those of KD [3]. Recent studies have indicated that patients with KD who had previously had COVID-19 were more likely to be resistant to IVIG treatment, to experience shock, and to have a decreased left ventricular ejection fraction than did those without evidence of preceding COVID-19 [6,7]. MIS-C may occur in individuals with SARS-CoV-2 infection, even if they display no symptoms [8]. However, the cardiac function and vascular damage in patients with KD after asymptomatic SARS-CoV-2 infection remain unclear. We investigated the clinical features and laboratory findings of patients with KD who had a history of COVID-19 and those who tested positive for anti-SARS-CoV-2 antibodies, including children with asymptomatic SARS-CoV-2 infection.