SAPHO syndrome: a followup study of 19 cases with special emphasis on enthesis involvement.
OBJECTIVE: To study the natural history, prognosis, and nosology of synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome. METHODS: We performed clinical, radiological, and biological reassessment of 19 cases of SAPHO syndrome (13 with pustulosis palmaris et plantaris, 3 with acne, 3 with no dermatological manifestations) after a mean disease course of 12.3 yrs (1-35). RESULTS: Similar involvement was noted in all patient groups. Despite persistent remittent attacks in 11/19 cases and new localizations in 10/19, the prognosis is promising and 18/19 patients considered that improvement has occurred. Enthesis involvement, occasionally associated with osteolysis, was in most cases the first event leading to hyperostosis, but tended to disappear in the spine and peripheral joints once synostosis was achieved. The behavior of osteochondral cartilage was similar to that of the enthesis, whereas the ribs below T6 were spared. We report the first descriptions of hyperostosis of the first costotransversal joint, interspinal ossification, erosion of wrist bones, followed by synostosis, and formation of bony bridges between ribs. CONCLUSION: SAPHO syndrome appears to be a relevant disease process with good prognosis. Although aseptic osteitis is regarded as the hallmark of this entity, our followup study strongly suggests that the initial disease targets are enthesis and related tissues. Forty-three percent of our patients met criteria of the European Spondyloarthropathy Study Group for spondyloarthropathy, but only one had the HLA-B27 phenotype. Thus, it may be considered that SAPHO syndrome is nosologically related to spondyloarthropathy, especially those types associated with psoriasis, but probably differs in pathogenesis.