Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis (SAPHO) Syndrome Mimicking Bone Metastases in the Spine: A Presentation of Two Cases and Literature Review.

Synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome is a rare disorder of unknown etiology with heterogeneous clinical manifestations. We describe two cases of patients diagnosed with SAPHO syndrome mimicking spinal bone metastases. A literature review was conducted to identify similar previously reported cases. The first patient was a 56-year-old woman with progressive back pain for six months who was referred to the neurosurgery department for suspected spinal metastases. A spinal CT scan revealed hyperdense lesions at T10 and hyperdense changes in the lumbar vertebrae. Spinal MRI demonstrated bone marrow edema that was hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging in multiple thoracic vertebrae, and the PET/CT showed multiple skeletal lesions affecting the spine with low-to-moderate 18F-FDG uptake. Scintigraphy showed the characteristic "bull's head" sign with increased uptake in the manubrium and bilateral sternoclavicular joints. The second patient was a 66-year-old woman with a four-month history of back pain, who was admitted with multiple spinal lesions. The diagnosis was made after bone scintigraphy demonstrated the characteristic findings of the syndrome. Both patients lacked cutaneous lesions on presentation but reported previous skin lesions. SAPHO syndrome is a rare condition, and bone lesions associated with the disease may be misdiagnosed as bone metastases. Knowledge of the syndrome and its imaging findings is essential for accurate diagnosis and treatment.