Spondylodiscitis in SAPHO syndrome. A series of eight cases.

OBJECTIVE To determine the frequency, clinical features, and radiological and bone scintigraphic changes of spondylodiscitis in patients with SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis). METHODS The study was retrospective. Data from patients with the diagnostic criteria of SAPHO syndrome were analysed for clinical features, biological data (HLA B antigen), and pelvic and spine x rays. Spine computed tomography (CT) or magnetic resonance imaging (MRI) were also examined in some cases. RESULTS 25 patients with a diagnosis of SAPHO were seen since 1985. Eight had spondylodiscitis. These included five with palmoplantar pustulosis, one with pustular psoriasis, one with psoriasis vulgaris, and one with chronic recurrent multifocal osteomyelitis without skin disease. The skin lesion occurred before the spondylodiscitis in four cases. Chest wall involvement was observed in four cases and sacroiliac joint lesions only in the case with osteomyelitis. HLA B27 was always negative and HLA B8 was found in four cases. Radiological findings consisted of erosive or sclerosing remodelling of endplates with a narrowed disc space; a reduced height of the vertebral body was also observed in some cases. These spinal lesions occurred in the three vertebral segments. Multiple sites of spondylodiscitis in the same patient were common. Bone scan showed mildly increased uptake and CT and MRI were useful for detecting signs of infection such as abscess. Enhanced signals on T2 weighted sequence or after injection of gadolinium were often observed. Follow up study of most of these patients suggests that the prognosis of spondylodiscitis in the SAPHO syndrome is favourable. CONCLUSIONS Despite few description in the literature, spondylodiscitis in the SAPHO syndrome is common (32% in this series). These radiological findings are similar to the discovertebral changes of spondylodiscitis in ankylosing spondylitis, thus giving support to the relations between SAPHO syndrome and spondylarthropathies. However, this does not mean that the pathogenic mechanisms are the same in these two conditions.