Osamu Arisaka1, Go Ichikawa1, Satomi Koyama2, Sairenchi Toshimi3. 1. Department of Pediatrics, Nasu Red Cross Hospital, Ohtawara, Tochigi-ken, Japan. 2. Department of Pediatrics, Dokkyo Medical University School of Medicine, Mibu, Tochigi-ken, Japan. 3. Department of Public Health, Dokkyo Medical University School of Medicine, Mibu, Tochigi-ken, Japan.