Characteristics of Pyomyositis at a Pediatric Hospital in Osaka, Japan.

Introduction Pyomyositis, also known as tropical pyomyositis, has traditionally been considered more prevalent in tropical regions. The number of pediatric pyomyositis cases has been increasing in several temperate countries. In this study, we examined the characteristics of pyomyositis in a single pediatric hospital in Japan, a temperate country. Methods We analyzed 108 patients diagnosed with pyogenic arthritis, pyogenic osteomyelitis, and pyomyositis who were followed up at our hospital over a 32-year period. Data were collected on sex, age of onset, affected site, causative organism, and year of occurrence. The characteristics of pyomyositis were identified through comparison with pyogenic osteomyelitis and pyogenic arthritis. Results The number of patients with pyogenic osteomyelitis, pyogenic arthritis, and pyomyositis was 44, 51, and 13, respectively. In pyogenic arthritis, the hip joint was the most commonly affected site (24 of 51 patients, 47.1%), where the femur was the most frequently involved site in osteomyelitis (14 of 44 patients, 31.8%). Among 13 patients with pyomyositis, 12 (92.3%) had muscle involvement around the hip joint, with the obturator muscles being the most commonly affected. Bacterial organisms were identified by venous blood or pus culture in 11 pyomyositis patients, with methicillin-sensitive