Background: The last nationwide survey of Kawasaki disease in Japan was conducted in 2003; the epidemiologic features of the disease in Japan since then are unknown.
Methods: All the hospitals with a pediatric department and a bed capacity of > or =100, or hospitals having a bed capacity of <100 but specializing in pediatrics in Japan were asked to report (by mail) all patients with Kawasaki disease who visited the hospital due to the disease in 2003 and 2004.
Results: Of the 2335 hospitals asked to participate, 1058 reported 19,138 patients with Kawasaki disease during the 2 year period 2003-2004. The annual incidence in 2004 reached 174.0 per 100,000 children under 5 years of age. The yearly number of patients and annual incidence increased significantly after the last nationwide epidemic of the disease in 1986. The number of patients was largest in January and lowest in October. The age-specific incidence was highest for those aged 9-11 months, and 88.9% of the patients were under 5 years of age. Of the reported patients, 2595 (13.6%) had cardiac lesions in the acute phase of the disease and 844 (4.4%) had cardiac sequelae 1 month after the onset of the disease.
Conclusion: The number of patients and the incidence of Kawasaki disease in Japan has increased year by year in the last two decades.