Idiopathic primary sternal osteomyelitis in an otherwise healthy patient.

Primary sternal osteomyelitis (PSO) is an exceptionally rare infection of the sternum, typically occurring in the context of trauma, surgery or immunocompromise. We report the case of a previously healthy adolescent boy in his second decade of life presenting with fever, chest pain and localised tenderness without any identifiable risk factors. Initial workup, including a chest X-ray and echocardiogram, was unremarkable, but persistent bacteraemia with methicillin-sensitive Staphylococcus aureus prompted further imaging. MRI revealed sternal osteomyelitis with a small parasternal abscess. The patient was successfully treated with intravenous antibiotics alone, avoiding surgical intervention. This case highlights the importance of thorough physical examination and maintaining a high index of suspicion for PSO in patients with unexplained fever and chest wall tenderness, even in the absence of traditional risk factors. Early diagnosis and targeted therapy are essential to optimise outcomes in this rare condition.