ANEURYSMAL BONE-CYST OF THE SACRUM

We describe the case of a 9-year-old girl presenting with a 3 month hi story of ingravescent pain in the sacro-iliac joint. The initial diagn osis was infective sacroiliitis and antibiotic therapy was started. As this therapy failed, computed tomography (CT) and magnetic resonance imaging (MRI) were performed, showing a roundish irregular mass with p olylobate edges and apparently haemorrhagic contents. The suspected di agnosis of aneurysmal bone cyst was confirmed histologically after sur gical excision of the mass. This case points to the risk of delayed di agnosis of the cause of pathological bone pain, which should be invest igated with the appropriate radiological techniques, since correct dia gnosis is crucial to prognosis.