When fever comes first: an unusual presentation of chronic non-bacterial osteomyelitis

Chronic non-bacterial osteomyelitis (CNO) is a rare, autoinflammatory bone disorder that primarily affects children and adolescents. Bone pain is its hallmark, though other symptoms may occur. The gradual onset and variable presentation make CNO difficult to diagnose and can delay treatment. Notably, systemic signs such as fever or weight loss are recognised but less common manifestations of the disease and are rarely the initial complaint.We report an adolescent male with two weeks of daily fevers, rigours, night sweats, headaches and weight loss. Bone pain appeared later, intermittently affecting multiple joints. Ultimately, MRI and bone biopsy results supported an autoinflammatory process. Symptoms and inflammatory markers improved with non-steroidal anti-inflammatory drugs, supporting the diagnosis of CNO.This case emphasises the atypical presentation and highlights the need to consider CNO in children with prolonged fever of unclear origin, even when bone pain is not the presenting symptom.