Factors Associated With Shock at Presentation in Kawasaki Disease Versus Multisystem Inflammatory Syndrome in Children Associated With Covid-19

Background: While clinical overlap between Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) has been evident, information regarding those presenting with shock has been limited. We sought to determine associations with shock within and between diagnosis groups. Methods: The International KD Registry enrolled contemporaneous patients with either KD or MIS-C from 39 sites in 7 countries from January 1, 2020, to January 1, 2023. Demographics, clinical features and presentation, management, laboratory values, and outcomes were compared between the diagnosis and shock groups. Results: Shock at presentation was noted for 19 of 672 KD patients (2.8%) and 653 of 1472 MIS-C patients (44%; P < 0.001). Within both groups, patients with shock were significantly more likely to be admitted to the intensive care unit, to receive inotropes, and to have greater laboratory abnormalities indicative of hyperinflammation and organ dysfunction, including abnormal cardiac biomarkers. Patients with KD and shock had a greater maximum coronary artery z score (median +2.62) vs KD patients without shock (+1.36; P < 0.001) and MIS-C patients with shock (+1.45 [vs +1.32 for MIS-C patients without shock]; P < 0.001). They were also more likely to have large coronary artery aneurysms. In contrast, MIS-C patients with shock had lower left ventricular ejection fraction (mean 51.6%) vs MIS-C patients without shock (56.6%; P < 0.001) and KD patients with shock (56.7% [vs 62.8% for KD patients without shock]; P = 0.04). Conclusions: Although patients with KD presenting with shock are clinically similar to patients with MIS-C, especially those with shock, they have more severe coronary artery involvement, whereas MIS-C patients with shock have lower left ventricular ejection fraction.