SAPHO syndrome: MR appearance of vertebral involvement

Purpose: To retrospectively evaluate the magnetic resonance ( MR) imaging findings of vertebral involvement in patients with synovitis, acne, pustulosis, hyperostosis, and osteitis ( SAPHO) syndrome. Materials and Methods: Ethics committee approval and informed patient consent were not required for this retrospective study. MR images obtained in 12 patients ( seven female, five male; mean age, 42 years; range, 16-65 years) with SAPHO syndrome involving the spine were reviewed. One vertebral lesion separated by one or more normal vertebrae was analyzed as a distinct lesion. For each lesion, the number of associated vertebrae with abnormal signal intensity ( SI) ( ie, single vertebra, two adjacent vertebrae, or more than two adjacent vertebrae) was noted. The following MR imaging findings were evaluated: cortical bone erosion, abnormal vertebral body SI compared with normal vertebral body SI, increased anteroposterior diameter of the vertebral body, soft-tissue involvement, vertebral body height loss of more than 30%, and abnormal SI of the adjacent intervertebral disk compared with the SI of the other disks. Results: Of 24 vertebral lesions found, 17 involved a single vertebra, four involved two adjacent vertebrae, and three involved three or four adjacent vertebrae. Vertebral corner cortical erosion was present in all lesions, and 23 ( 96%) lesions had anterior vertebral corner involvement. The erosion was confined to a vertebral corner in five ( 21%) lesions and included the adjacent endplate and/or the anterior cortex of the vertebral body in the remaining 19 ( 79%) lesions. In four ( 17%) lesions, involvement of two adjacent vertebral corners on either side of an intervertebral disk mimicked to some extent early disk space infection. An adjacent disk space was narrowed in six ( 25%) lesions and exhibited abnormal SI in two ( 8%). Prevertebral tissue thickening was observed in eight ( 33%) lesions. Conclusion: Erosion of a vertebral body corner is consistently seen on MR images of SAPHO vertebral lesions and may support the diagnosis of SAPHO syndrome in the appropriate clinical context.