Psoas Muscle Abscess and Sacroiliitis Due to MSSA Bacteremia in a Healthy Adolescent

Abstract Psoas muscle abscess and infectious sacroiliitis are rare causes of hip pain and fever in pediatric patients. We report the case of an 11-year-old previously healthy girl who presented with gluteal pain, claudication, and fever. Initial ultrasound and computed tomography were inconclusive, but magnetic resonance imaging revealed a left psoas muscle abscess measuring 40 × 18 × 30 mm and associated infectious sacroiliitis. Methicillin-sensitive Staphylococcus aureus (MSSA) was isolated from blood cultures. Given the favorable clinical evolution under empirical intravenous flucloxacillin, the patient was managed conservatively without surgical drainage. She completed a 6-week antibiotic regimen, with complete clinical recovery and radiologic resolution of the abscess. This case highlights the importance of early imaging and blood cultures in children with persistent hip pain and fever and supports conservative management as a valid and effective option for selected pediatric patients with psoas muscle abscesses.