Chronic recurrent multifocal osteomyelitis mimicking osteoid osteoma.

In this article we illustrate an unusual case of chronic recurrent multifocal osteomyelitis (CRMO) in a 9 year old girl who presented with right thigh pain. The initial plain radiographs were normal. The white cell count was normal and there was a mild rise in C-reactive protein. Cross sectional imaging of the right femur showed a lesion with features suggestive of osteoid osteoma. However, when the lesion was excised, the appearances on histopathological examination were non-specific showing chronic inflammatory cells and the microbiological testing revealed no organisms. Six months later, this child presented with right shoulder pain and the subsequent imaging demonstrated bilateral clavicular lesions. At this stage, the diagnosis of CRMO was made based on the combination of the clinical, radiological, histopathological and microbiological features. This case demonstrates that the cross sectional imaging features of the bony lesion in CRMO can mimic osteoid osteoma.