Objective Epidemics of Kawasaki disease (KD) are well known; however, the seasonal variation in the clinical course of KD is uncertain. The aim of this study was to investigate the seasonality in the clinical course of KD.

Methods This study included 744 patients who were admitted to six hospitals in Kitakyushu City for KD from 2010 to 2014. We divided the patients into two groups according to the average monthly temperature (warm and cold periods) and compared the clinical courses of KD.

Results The clinical courses of 715 patients who were initially treated with intravenous immunoglobulin (IVIG) were investigated. The proportion of patients with resistance to the initial IVIG therapy was significantly higher during the warm period than during the cold period (p=0.016). There was no seasonality in the proportion of patients with coronary artery abnormalities.

Conclusion Seasonality was observed in the response to IVIG therapy of patients with KD.