Characteristic Imaging Findings and Diagnostic Value of SAPHO Syndrome: A Report of 6 Cases and Literature Review

Objective To investigate the characteristic imaging findings of Synovitis, Acne, Pustulosis, Hyperostosis, and Osteitis (SAPHO) syndrome and to improve diagnostic accuracy for this rare disease, thereby reducing misdiagnosis and missed diagnosis. Methods Clinical and imaging data (including CT and MRI) of 6 patients with SAPHO syndrome admitted to our hospital between November 2011 and August 2025 were retrospectively analyzed. The distribution patterns and imaging characteristics of the lesions were summarized. Results All 6 patients had involvement of the anterior upper chest wall, with 4 cases showing the typical "bull's head sign". A total of 144 vertebral bodies were evaluated for spinal involvement. CT detected abnormalities in 34 vertebrae (23.6%), while MRI detected abnormalities in 51 vertebrae (35.4%), with the thoracic spine being the most commonly affected site (73% on CT, 62.7% on MRI). Characteristic spinal findings included the "shiny corner sign", "semicircular sign", "round sign", and "kissing sign". Sacroiliac joint involvement was present in 3 patients. Three of the 6 patients had been initially misdiagnosed. Conclusion Skeletal lesions in SAPHO syndrome predominantly affect the anterior chest wall, spine, and sacroiliac joints. The "bull's head sign" in the anterior chest wall and specific signs along the anterior vertebral margins of consecutive vertebrae (such as the "shiny corner sign" and "kissing sign") hold significant diagnostic value. Familiarity with these characteristic imaging features, combined with the presence of skin lesions, can assist clinicians and radiologists in achieving early and accurate diagnosis of SAPHO syndrome.