A 4-year-old boy was referred to our hospital with chief complaints of fever and leg pain. His body temperature was 38.8°C. He had spontaneous pain in the medial aspects of both thighs, which worsened with external and internal rotation. Blood tests revealed elevated C-reactive protein levels and erythrocyte sedimentation rate. Upon admission, a musculoskeletal infection was suspected, and cefazolin sodium was initiated. On day 4 of hospitalization, Salmonella enterica subsp. enterica serovar Enteritidis (O9) was detected in a blood culture. Magnetic resonance imaging revealed myositis of the lower extremities. Accordingly, the patient was diagnosed with infectious myositis. Cefazolin sodium was changed to ceftriaxone due to drug susceptibility. A second blood culture was negative, and the patient was discharged from the hospital on day 18 of illness with no recurrence of symptoms. Remission has been maintained following discharge. Pediatric myositis can be classified as bacterial, viral, or autoimmune. Gram-positive cocci are the most common causative organisms, and hematogenous spread is the most common route of infection in children. In this case, the bacterial culture and clinical findings indicated that the myositis was associated with a hematogenous Salmonella infection originating from the intestinal tract. A history of gastrointestinal disease and culture collection are important for accurate diagnosis of pediatric myositis.
