Osteoid osteoma in a 16-year-old boy presenting with atrophy of the left thigh: diagnostic difficulties.

Osteoid osteoma is an osteoblastic benign lesion of the bone. The pathognomonic symptom is significant pain, which responds well to nonsteroidal antiinflammatory drugs. When typical clinical and radiological features are present, the diagnosis is not difficult. However, if the lesion is in an area not clearly seen on plain radiographs, or clinical features are atypical, then diagnosis becomes difficult. We present a case of osteoid osteoma with delayed diagnosis that presented itself with neurological signs. Prominent features present in the patient included pain that responded well to medication and muscle atrophy, which led to a wider differential diagnosis. Diagnosis was made approximately two years after the onset of his initial symptoms, after having been investigated and treated both in our own hospital and elsewhere. This case illustrates clinical and radiological diagnostic problems of osteoid osteoma, demonstrating that it can present itself with neurological signs. Correct diagnosis then requires detailed history and clinical awareness.