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.