Spectrum of Coronary Artery Involvement With Multisystem Inflammatory Syndrome in Children Versus Kawasaki Disease

Background: There is significant overlap in clinical features between multisystem inflammatory syndrome in children (MIS-C) and Kawasaki disease (KD). We sought to compare the prevalence, severity, and associated factors for coronary artery (CA) involvement. Methods and Results: From January 1, 2020 through January 31, 2023, 1191 patients with MIS-C and 554 patients contemporaneously diagnosed with KD were enrolled into the International Kawasaki Disease Registry. Demographic and clinical features, laboratory values, maximum Z score in any CA branch at any time point, and worst left ventricular ejection fraction, were compared between groups. Factors associated with CA aneurysms (maximum Z score in any CA branch +2.5 or greater) were determined separately for each diagnosis using multivariable logistic regression analyses. The prevalence of CA aneurysms was lower for MIS-C versus KD (16% versus 25%, respectively; P<0.001) and less severe by size category (1.2% with medium/large CA aneurysm versus 9.6%, respectively). Male sex and lower nadir hemoglobin levels were associated with greater odds of CA aneurysms for both groups. Additional associated factors for KD patients included age<6 months, fewer clinical KD criteria (more incomplete presentation), presentation with shock, and greater total days of fever. There were no additional associated factors for patients with MIS-C. Using exploratory splines, there was a trend of improvement in Z scores within 30 days of illness for both MIS-C and KD for CA involvement other than large aneurysms. Conclusions: CA involvement for patients with MIS-C was less prevalent and milder in severity compared with contemporaneous patients with KD, with fewer associated factors, and a high prevalence of regression to a normal luminal dimension.