La sacro-iliite à pyogène est rare chez l’enfant. L’abcès du muscle iliopsoas en constitue une complication exceptionnelle. Nous rapportons le cas d’une fille, âgée de 12 ans, hospitalisée pour fièvre et douleur de la fosse iliaque gauche avec psoïtis évoluant depuis 21 j. La tomodensitométrie permettait de faire le diagnostic d’une sacro-iliite à pyogène compliquée d’un abcès de l’iliopsoas. Le traitement consistait en une antibiothérapie associée à un drainage chirurgical de l’abcès.

Pyogenic sacroiliitis is a rare entity in children. Diagnosis is often delayed because of its variable clinical presentation, low suspicion by the examining physician, and rare findings on radiographs. Delayed diagnosis, however, results in complications such as iliopsoas abscess. We report the case of a 12-year-old girl hospitalized with a 21-day history of fever, pain in the left iliac fossa, and flexion contracture of the hip. On examination, she had fever (38.9 °C), psoitis, localized tenderness at the left sacroiliac joint, and pain elicited by lateral compression of the pelvis. The abdominal examination was normal. The erythrocyte sedimentation rate was 130mm in the first hour, C-reactive protein was 186mg/l, and the white blood cell count was 18,400/mm³, with 79% neutrophils. Urinalysis was normal. Blood cultures were negative. Radiographs of the pelvis showed irregular left sacroiliac borders. The CT scan provided the diagnosis of sacroiliitis complicated by an ilioapsoas abcsess. Treatment was based on antibiotic therapy associated with surgical drainage. Bacteriologic investigation revealed Staphylococcus aureus. The patient’s temperature returned to normal on the second day. Antibiotics were continued for 3 months, leading to full recovery.