Unilateral infective sacroiliitis in a boy presenting with a limp

A 9-year-old boy admitted to a district general hospital with a 1-week history of fever and a 2-day history of right hip pain. Initial workup revealed raised inflammatory markers and unremarkable imaging studies. After clinical review, there was minimal improvement of the patient’s condition 5 days after presentation; therefore, an MRI of the pelvis/hips was carried out, which supported a clinical diagnosis of right-sided infective sacroiliitis. Infective sacroiliitis is rare and only represents 1%–2% of septic arthritis in children. The condition still remains a diagnostic challenge first due to poor localisation of symptoms with referred pain to the hip, thigh and lower back and second due to a lack of awareness by non-specialist clinicians. Early diagnosis is a key to avoid sequelae such as an abscess, degenerative changes of the sacroiliac joint and can be achieved by a thorough clinical examination, monitoring inflammatory markers and MRI.