[Chronic monoarthritis caused by osteoid osteoma].

Osteoid osteoma is a nonmalignant tumour that rarely localizes intraarticularly. When this happens, the tumour provokes arthritis and its recognition is delayed from months to years. We report the case of a 34 year old man with a previously known HIV infection, but no evidence of immunosuppression. He develops a chronic monoarthritis of the left elbow that is initially interpreted as infectious disease. CT provides diagnostic suspicion of osteoma, that is confirmed by pathologic examination two years after the onset of the clinical complaints. CT is the radiologic technique of election in the evaluation of osteoid osteoma. Synovitis is interpreted in the literature as secondary to prostaglandin secretion by the tumour.