Multimodal imaging findings of SAPHO syndrome with no skin lesions: A report of three cases and review of the literature.

Synovitis, acne, palmoplantar pustulosis, hyperostosis and osteitis syndrome (SAPHO) is a rare syndrome that affects the skin, bones and joints. Diagnosis of SAPHO syndrome is established on clinical appearance and imaging features. The present case report described the imaging features of three cases of SAPHO with sternoclavicular joint arthritis but without skin manifestations using multiple imaging modalities, including computed tomography (CT), magnetic resonance imaging (MRI) and bone scintigraphy. The first case was a 52-year-old male who suffered from progressive sternoclavicular arthritis for 2 years. The second case was a 62-year-old female with arthritis in the larger joints for 5 years, particularly on the right thoracic area. The third case was a 44-year-old male who exhibited a slight bulge accompanied by pain in the upper anterior chest wall for 4 years. All of them lacked cutaneous lesions. CT demonstrated sclerosis and hyperostosis with subchondral erosions in the sternocostoclavicular joints. MRI revealed bone marrow edema that was slightly hypointense on T1-weighted imaging, and hyperintense on T2-weighted imaging. Typical 'bull head' signs were observed in bone scintigraphy images. The present case study demonstrated that SAPHO syndrome should be suspected in patients with multifocal osteitis or arthritis affecting the chest wall that lack skin manifestations. Multimodal imaging modalities in combination are helpful for SAPHO diagnosis.