Similarities and Differences between Multisystem Inflammatory Syndrome in Children (MIS-C) and Kawasaki Disease Shock Syndrome

Abstract

This study aimed to investigate the characteristics of COVID-19-associated multisystem inflammatory syndrome in children (MIS-C) and Kawasaki disease shock syndrome (KDSS) and to compare the similarities and differences between the two diseases. The incidence of KDSS and MIS-C was also estimated. Medical records of patients diagnosed with MIS-C or KDSS at four hospitals from January 2013 to December 2022 were retrospectively reviewed. Thirty-one patients were enrolled in the study in either an MIS-C group (n = 22) or a KDSS group (n = 9). The incidence of KDSS in KD was 0.8% (9/1095) and the incidence of MIS-C versus KD was 10.2% (22/216). Compared with the MIS-C group, the KDSS group had longer hospital stays and more severe systemic inflammation (e.g., anemia, elevated C-reactive protein, hypoalbuminemia, and pyuria) and organ dysfunction (e.g., number of involved organs, shock, vasoactive infusion, and intensive care unit admission). All patients in the MIS-C group, but none in the KDSS group, including two patients during the COVID-19 pandemic, had laboratory evidence of SARS-CoV-2 infection. MIS-C and KDSS shared demographic, clinical, and laboratory characteristics; organ dysfunction; treatment; and outcomes. Overall severity was more severe in patients with KDSS than in those with MIS-C. The most important difference between MIS-C and KDSS was whether SARS-CoV-2 was identified as an infectious trigger.

Keywords: Kawasaki disease; Kawasaki disease shock syndrome; multisystem inflammatory syndrome in children.

Figure 1

The annual (first- and second-half) incidences of KDSS and MIS-C compared with KD. A total of 9 patients with KDSS were hospitalized during the 10-year study period (i.e., pre-COVID-19 pandemic + COVID-19 pandemic) and 22 patients with MIS-C were hospitalized during the COVID-19 pandemic. Dividing by the number of patients with KD, the incidence of KDSS was 0.8% (9/1095) and the incidence of MIS-C was 10.2% (22/216). COVID-19, coronavirus disease 2019; KDSS, Kawasaki disease shock syndrome; MIS-C, multisystem inflammatory syndrome in children; KD, Kawasaki disease.

Figure 2

Relationships between KD, KDSS, and MIS-C. (A) KD is characterized by KD-like features and systemic inflammation. Infectious triggers are expected to play an important role in the pathogenesis of KD. (B) KDSS is diagnosed when shock presenting as organ dysfunction is observed in patients with KD-like features and systemic inflammation. (C) MIS-C is diagnosed when SARS-CoV-2 is identified in patients with KD-like features, systemic inflammation, and organ dysfunction such as shock. SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; KD, Kawasaki disease; KDSS, Kawasaki disease shock syndrome; MIS-C, multisystem inflammatory syndrome in children.