AB1453 INFLAMMATION MARKERS, SYSTEMIC INFLAMMATORY BASED SCORES (SIBS) AND CYTOKINE PROFILES IN ADULT CHRONIC NONBACTERIAL OSTEOMYELITIS (CNO)/SAPHO SYNDROME: AN IMMUNOLOGICAL CHARACTERIZATION

Background Chronic non-bacterial osteomyelitis (CNO) is a rare bone disease occurring in children and adults. Adults mainly present with osteitis hyperostosis of the anterior chest wall, sometimes context synovitis, acne, pustulosis, hyperostosis, (SAPHO) syndrome [1]. CNO hypothesized to be an auto-inflammatory disease, as studies on pediatric patients have shown raised erythrocyte sedimentation rate (ESR) C-reactive protein (CRP), elevated serum concentrations interleukin (IL)-6, 8, 17A TNF-a [2]. For adults, however, suspected systemic immune activation not consistently reflected by these generic markers, data cytokine expression are scarce variable [3, 4]. Objectives To provide broad immunological characterization adult CNO/SAPHO, including profiles, compared controls. Methods Cross-sectional study our referral center CNO/SAPHO active (n=172) controls (n=82) referred between 1992-2022 using immunomodulatory treatment (exempting NSAIDs) or bisphosphonates. Generic inflammation parameters inflammatory based scores (SIBS) were without concomitant arthritis/dermatitis, strong moderate increase isotope uptake nuclear imaging. Serum levels Th1/2 Th17-derived cytokines determined electrochemiluminescent immunoassays, receptor activator factor kappa beta (RANKL) osteoprotegerin (OPG) ELISA 33 8 Results ESR, CRP, platelet, leucocyte neutrophil count higher than controls, but generally remained within reference range. ESR was also arthritis/dermatitis isolated (24 versus 16, p=0.009 ), strongly rather moderately increased imaging (20 13, p= 0.009 ). Neutrophil-derived SIBS (neutrophil/lymphocyte ratio (NLR) index (product NLR platelet count)) Cytokine analyses revealed no differential for IL-6, -8, -10, -13, -17A, -22, -23, -27, TNF-a, IFN-γ, MIP-3a, nor markers RANKL osteoprotegerin. Conclusion In this cohort, neutrophil-derived SII contrast previous studies, we found -17A support imbalance CNO/SAPHO. Further needed evaluate whether hypothesis applies much subtype, if so, local inflammasome systemically reflected. References [1]Leerling A, Dekkers O, Appelman-Dijkstra N, Winter E. Clinical therapeutic diversity chronic nonbacterial sternocostoclavicular region: meta-analysis. Rheumatology (Oxford). 2022. [2]Buch K, Thuesen ACB, Brons C, Schwarz P. Non-bacterial Osteomyelitis: A Review. Calcified Tissue International. 2019;104(5):544-53. [3]Zhang S, Li Zhang L, W, Dong Z, et al. proinflammatory, anti-inflammatory cytokines, RANKL/OPG syndrome. Modern rheumatology. 2019;29(3):523-30. [4]Przepiera-Bedzak H, Fischer Brzosko M. IL-6 IL-23 Levels Their Correlation Angiogenic Cytokines Disease Activity Ankylosing Spondylitis, Psoriatic Arthritis, SAPHO Syndrome. Mediators Inflamm. 2015;2015(2):785705-7. Acknowledgements: NIL. Disclosure Interests None Declared.