<h3>Background:</h3> Axial Spondyloarthritis (axSpA) represents an inflammatory disorder primarily affecting the axial skeleton, peripheral joints, and enthesis. The severe form of axSpA is ankylosing spondylitis (AS), distinguished by significant bone damage. Joint pain, stiffness, and functional impairment precipitate diminished physical activity and adoption of a sedentary lifestyle. The persistent inflammation and decreased physical activity contribute to complications such as osteoporosis and potentially sarcopenia, denoting a condition characterized by low muscle mass, diminished strength, and impaired physical performance. Despite the anticipated higher prevalence of sarcopenia in individuals with AS, existing evidence remains inconclusive, primarily due to study heterogeneity and the utilization of outdated criteria. <h3>Objectives:</h3> This systematic literature review seeks to identify and critically evaluate pertinent studies concerning compromised muscle health in AS, taking into account the most recent pathophysiological mechanisms that interconnect bone, enthesis, joints, and muscles. The objective is to reevaluate the influence of diminished muscle mass and strength on the progression of AS, thereby instigating potential future investigations and targeted interventions aimed at enhancing patient functionality and overall quality of life. <h3>Methods:</h3> This review adheres to PRISMA guidelines. The Scopus, PubMed, and Web of Science databases were searched for articles on muscle mass, muscle strength and axSpA. The methodological quality of the studies included in the review was evaluated using the Newcastle-Ottawa Scales for observational studies and for case-control studies. Inclusion criteria were: (a) studies investigating the relationship between muscle mass and muscle strength, and axSpA, comparing patients to healthy controls or different rheumatic disease; (b) population aged ≥18 years; (c) defined and validated criteria to assess the presence of sarcopenia; and (d) English language and availability of full text of the original research paper. <h3>Results:</h3> A total of 190 papers were identified through the searches, with 14 meeting the inclusion criteria, forming a global cohort of 1233 AS patients. Among these, 1 study was prospective, while 11 were case-control studies, and 2 were cross-sectional studies. Methodological approaches to assess muscle mass and strength exhibited heterogeneity across the studies, with varied techniques employed for evaluating appendicular and truncal mass and strength. Rather than the explicit diagnosis of sarcopenia, pre-sarcopenia or probable sarcopenia was frequently observed in subjects with AS, characterized by a significant reduction in muscle strength, particularly in the lower limbs. The status of pre-sarcopenia appears to be associated with elevated AS disease activity, implying that inflammation leading to pain, restricted movement, and diminished physical activity may play a pivotal role in the muscular health of AS patients. <h3>Conclusion:</h3> Our review confirms the presence of a correlation between AS and the decline in muscle strength, likely indicative of sarcopenia, even in patients of a young age. While the exact mechanisms contributing to muscle damage remain a subject of debate, factors such as inflammation, diminished physical activity, a sedentary lifestyle, glucocorticoid therapy, and neuromuscular impairment may play significant roles (refer to <b>Figure 1</b>). Effectively managing AS patients necessitates a multidisciplinary non-pharmacological approach, emphasizing the early implementation of physical therapy and rehabilitation programs, as bDMARDs alone prove insufficient for the restoration of optimal muscle health. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>

AB0905 IS SARCOPENIA A REAL PROBLEM IN PATIENTS WITH ANKYLOSING SPONDYLITIS? A SYSTEMATIC LITERATURE REVIEW