Osteoid osteoma of the calcaneum: a small painful lesion causing confusing symptoms.

An 8-year-old girl presented with left ankle pain and limping for 1 month. There was no history of trauma or febrile illness. Her medical history was unremarkable, and there was no family history of rheumatism. Physical examination revealed mild soft tissue swelling and tenderness over the lateral aspect of the ankle and heel. No skin change, local warmth or focal mass was evident, but the range of ankle movement was limited by pain. The child’s symptoms did not improve after treatment with oral paracetamol or a topical heparinoid. Nocturnal pain was present but not typical. Inflammatory arthritis was once suspected. Blood tests revealed only a mildly elevated white cell count (16.7 x 109 /L), while the erythrocyte sedimentation rate, levels of Creactive protein, calcium and phosphate, and various autoimmune markers, as well as liver and renal biochemical test results were normal.