Diagnosing SAPHO Syndrome in Suspected Metastatic Bone Tumors

A previously healthy 44-year-old woman who had been followed at different health care facilities for symptoms which had begun 3 years earlier was referred to our service for clinical evaluation. Her problems during the initial examination were pain in the sternoclavicular and sacroiliac joints as well as plantar pustulitis. Based on previous x-ray hyperostosis findings, metastatic bone tumors to the spine and first costocondral junctions bilaterally were suspected. A biopsy of the sternoclavicular lesion showed a nonspecific inflammation pattern. On the first physical examination we found a nontender swelling of the sternoclavicular junctions, necrosis of the plantar epidermis and pain at the sacroiliac joints. The patient was referred for bone scintigraphy and positron emission tomography-computed tomography (PET-CT) scan. The whole body bone scintigraphy using Tc-99m MDP showed increased accumulation of the radiotracer in the anterior chest wall and in the right sacroiliac joint. Metastatic bone tumor was not suggested, although exclusion of bone metastases was difficult. The PET-CT with F-18 FDG showed areas with low metabolic activity in the anterior chest wall (SUV Max: 1.96) and in the right sacroiliac joint (SUV Max: 2.18) making the diagnosis of malignancy and acute infection unlikely. The clinical symptoms, the typical skin lesions involving the soles of the feet and low hypermetabolic lesions on PET-CT made the final diagnosis of SAPHO syndrome.