Syphilitic bone destruction on FDG PET/CT.

A 35-year-old man underwent PET/CT scan to evaluate suspected osseous metastases from a presumed tumor of unknown origin. PET images demonstrated multiple foci of increased FDG uptake in all extremities, corresponding to the osseous destruction on the concurrent CT images. However, no primary tumor was identified. Instead, the bone lesions were subsequently proven due to syphilis infection.