Abstract
IntroductionSynovitis-acne-pustulosis-hyperostosis-osteitis (SAPHO) syndrome is a rare disorder. The etiology remains unknown and the treatment is still empirical. Synovitis is one of the major manifestations, but information on histopathological features is still lacking. In this case, we investigated the histopathological features of SAPHO syndrome synovitis.Case presentationWe present the case of a 53-year-old Japanese woman with SAPHO syndrome accompanied by marked knee synovitis and palmoplantar pustulosis. We found abundant sterile joint fluid in the right knee, and a blood test showed abnormally high values of C-reactive protein (17.26 mg/dl) and matrix metalloproteinase-3 (800 ng/ml). Arthroscopic surgery revealed marked proliferation of villous synovial tissues similar to rheumatoid arthritis and standard microscopic findings were also similar to rheumatoid arthritis. Furthermore, for the first time, we demonstrated by immunohistochemistry the expression of tumor necrosis factor-alpha (TNF-α) converting enzyme, TNF-α and matrix metalloproteinase-3 in the proliferated synovial lining cells. After arthroscopic synovectomy, her knee symptoms immediately diminished and laboratory data (matrix metalloproteinase-3 and C-reactive protein) normalized within 2 weeks of surgery.ConclusionWe demonstrate the expression of TNF-α converting enzyme, TNF-α and matrix metalloproteinase-3 in SAPHO syndrome synovitis for the first time and also show, both macro- and microscopically, the similarity between SAPHO syndrome and rheumatoid arthritis synovitis. These new findings support the recently reported successful treatment of SAPHO syndrome with antirheumatic drugs, especially with anti-TNF-α agents.
Highlights
Synovitis-acne-pustulosis-hyperostosis-osteitis (SAPHO) syndrome is a rare disorder
For the first time, we demonstrated by immunohistochemistry the expression of tumor necrosis factor-alpha (TNF-a) converting enzyme, TNF-a and matrix metalloproteinase-3 in the proliferated synovial lining cells
We demonstrate the expression of TNF-a converting enzyme, TNF-a and matrix metalloproteinase-3 in SAPHO syndrome synovitis for the first time and show, both macro- and microscopically, the similarity between SAPHO syndrome and rheumatoid arthritis synovitis
Summary
Synovitis-acne-pustulosis-hyperostosis-osteitis (SAPHO) syndrome is a rare disorder characterized by osteoarticular and dermatological manifestations, and was first proposed by Chamot et al [1]. TNF-a converting enzyme (TACE) processes a membrane form of TNF-a to a soluble form [9], and the binding of the latter form to TNF receptors triggers pathological events in RA These findings indicate that synovitis and the processing of TNF-a by TACE are very important aspects in the pathogenesis of SAPHO syndrome. Primary antibodies used for these analyses were polyclonal antibodies for TACE (sc-25782; Santa Cruz Biotechnology, USA), TNF-a (654250; Calbiochem, Germany), monoclonal antibodies for MMP-3 (55-2A2; Daiichi Fine Chemical Co., Japan) and CD68 (M0814; DakoCytomation, Denmark). After arthroscopic synovectomy, her knee symptoms immediately diminished and laboratory data (MMP-3 and CRP) normalized within 2 weeks of surgery. In the 2-year follow-up period, there was no recurrence of synovitis, no exacerbation of palmoplantar pustulosis, and MMP-3 and CRP levels remained normal
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