RÉSUMÉ
OBJECTIVE: Kawasaki disease (KD) is a systemic vasculitis of young children that can lead to development of coronary artery aneurysms. We aimed to identify diagnostic markers to distinguish KD from other pediatric inflammatory diseases. METHODS: We used the proximity extension assay to profile proinflammatory mediators in plasma samples from healthy pediatric controls (n = 30), febrile controls (n = 26), and patients with KD (n = 23), multisystem inflammatory syndrome in children (MIS-C; n = 25), macrophage activation syndrome (n = 13), systemic and nonsystemic juvenile idiopathic arthritis (n = 14 and n = 10, respectively), and juvenile dermatomyositis (n = 9). We validated the key findings using serum samples from additional patients with KD (n = 37) and febrile controls (n = 28). RESULTS: High-fidelity proteomic profiling revealed distinct patterns of cytokine and chemokine expression across pediatric inflammatory diseases. Although KD and MIS-C exhibited many similarities, KD differed from MIS-C and other febrile diseases in that most patients exhibited elevation in one or more members of the interleukin-17 (IL-17) cytokine family, IL-17A, IL-17C, and IL-17F. IL-17A was particularly sensitive and specific, discriminating KD from febrile controls with an area under the receiver operator characteristic curve of 0.95 (95% confidence interval 0.89-1.00) in the derivation set and 0.91 (0.85-0.98) in the validation set. Elevation of all three IL-17-family cytokines was observed in over 50% of KD patients, including 19 of 20 with coronary artery aneurysms, but was rare in all other comparator groups. CONCLUSION: Elevation of IL-17 family cytokines is a hallmark of KD and may help distinguish KD from its clinical mimics.