Epidemiologic Features of Kawasaki Disease in Japan: Results of the 2009–2010 Nationwide Survey

BACKGROUND Although the number of patients and incidence rate of Kawasaki disease (KD) are increasing in Japan, the most recent epidemiologic features of KD are not known. METHODS The 21st nationwide survey of KD was conducted in 2011 and included patients treated for the disease in 2009 and 2010. Hospitals specializing in pediatrics, and hospitals with a total of 100 or more beds and a pediatric department, were asked to report all patients with KD during the 2 survey years. RESULTS A total of 1445 departments and hospitals reported 23,730 KD patients (10,975 in 2009 and 12,755 in 2010): 13,515 boys and 10 215 girls. The annual incidence rates were 206.2 and 239.6 per 100,000 children aged 0 to 4 years in 2009 and 2010, respectively; the 2010 rate was the highest ever reported in Japan. Monthly number of patients peaked during winter to spring months; lower peaks were noted during summer months. However, the seasonal patterns in 2009 and 2010 differed from those of previous years. The age-specific incidence rate had a monomodal distribution, with a peak during the latter half of the year of birth. The prevalences of cardiac lesions during acute KD and cardiac sequelae were higher among infants and older age groups. Despite a decrease in prevalence, the proportion of patients with giant coronary aneurysms-the most severe sequela of KD-did not substantially decrease. CONCLUSIONS The incidence rate and number of patients with KD continue to increase in Japan.