SAPHO-like bone scintigraphy in diffuse idiopathic skeletal hyperostosis: a case report

Background Bone scintigraphy is sensitive to increased osteoblastic activity but is not disease specific. Diffuse idiopathic skeletal hyperostosis (DISH) may therefore be mistaken for synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome when uptake involves the anterior chest wall and spine. Case presentation A 50-year-old woman presented with a 1-year history of painless left sternoclavicular prominence. She reported that her daughter had SAPHO syndrome with anterior chest wall pain and palmoplantar pustulosis. Whole-body 99mTc-MDP scintigraphy and single-photon emission computed tomography showed uptake in the left sternoclavicular joint and multiple cervical and thoracic vertebrae. However, the patient had no inflammatory pain, skin lesions, or marked systemic inflammatory response. A low-dose whole-spine CT demonstrated flowing anterolateral ossification across multiple contiguous thoracolumbar vertebrae with preserved disc spaces; a sacroiliac CT showed no erosive sacroiliitis. A sternoclavicular MRI showed no bone marrow edema. These findings supported DISH. During 3 years of follow-up, no skin disease or osteitis-related symptoms developed. Conclusion DISH should be considered when SAPHO-like scintigraphy is discordant with the clinical findings and CT/MRI evidence. A six-step approach integrating symptoms, skin findings, metabolic and medication history, MRI, CT, and follow-up may help assess this discordance, but this has not been validated.