ABS1071 MUSCULOSKELETAL MANIFESTATIONS OF ENTEROPATHIC ARTHRITIS VARY IN RELATION TO INFLAMMATORY BOWEL DISEASE BEHAVIOUR, LOCALIZATION, AND EXTENT

Background: Spondyloarthritis (SpA) and inflammatory bowel diseases (IBD), such as Crohn's disease (CD) and ulcerative colitis (UC) coexist in enteropathic arthritis (IBD-SpA), which is the less studied phenotype within the SpA spectrum. As such, despite fundamental advances are occurring across axial SpA and psoriatic arthritis, similar progress has not occurred within IBD-SpA and there is not an agreement on a clear recognition of clinical phenotypes (or domains). Conversely, CD and UC display different and well-defined characteristics with regard to disease phenotype, localization, and extent. At present, no data explore the possible musculoskeletal and extra-musculoskeletal differences of IBD-SpA according to IBD features. Objectives: The aims of the study were (1) to assess the demographic, clinical, and treatment differences between CD-SpA and UC-SpA, (2) to evaluate whether IBD features are associated with different SpA manifestations, (3) to compare CD-SpA patients with and without perianal involvement. Methods: We took advantage of the multidisciplinary SpA-IBD clinic within the ImmunoCenter of the Humanitas Research Hospital, Rozzano, and identified patients with coexisting diagnoses of SpA and IBD who were consecutively seen between March 2022 and March 2024. Patients with SpA were included if fulfilling the ASAS classification criteria for axial or peripheral SpA, while the CD or UC diagnosis was based on ECCO criteria. Demographic and clinical data were collected at baseline and at the last available follow-up visit; also, IBD patterns (CD, UC), and localization, extent, and behaviour of the disease were evaluated according to the Montreal classification criteria. CD was as inflammatory (B1), stenosing (B2), fistulizing (B3), with a possible perianal disease associated, with regard the behaviour, and as ileal (L1), ileo-colic (L3), colonic (L2), and/or upper GI (L4) with regard the localization. Similarly, the extent of UC can be limited to the rectum (E1) or be spread to the left (E2) or the whole colon (E3). SpA was defined based on the presence of peripheral arthritis, axial arthritis, combined peripheral-plus-axial, enthesitis, dactylitis, psoriasis, uveitis, and erythema nodosum. Isolated axial involvement was defined by the absence or peripheral joint involvement at last follow-up visit, and vice versa. Multi-drug failure was defined in patients who failed more than 2 b- or ts-DMARDs with different mechanisms of action. Results: We analysed 66 patients with IBD-SpA, the largest part (n=40) with CD and the remaining (n=26) with UC; no differences were observed between the two subgroups except for a higher frequency of psoriasis within the former [19 (47%) in CD vs. 6 (23) in UC; p=0.046] (Table 1). Among UC cases, extensive colitis was more commonly associated with combined peripheral-axial involvement [8 (61%) for E3 vs. 0 (0%) for E1 and 2 (22%) for E2; p=0.016]. With respect to CD, the isolated axial involvement was more common in patients with stenosing phenotype involvement [7 (41%) for B2 vs. 3 (15%) for B1 and 2 (40%) for B3; p=0.042] and colonic disease [8 (44%) for 2 vs. 3 (9%) for L1 and 0 (0%) for L1; p=0.010], while dactylitis was more frequently observed in those with fistulizing phenotype [2 (40%) for B3 vs. 2 (10%) for B1 and 1 (6%) for B2; p=0.017] and ileo-colic localization [2 (33%) for L3 vs. 4 (19%) for L1 and 3 (17%) for L2; p=0.039]. We did not observe differences comparing CD patients with and without perianal involvement except for a more common association with uveitis within the former [3 (43%) for perianal disease vs. 1 (3%) for non-perianal disease; p=0.00]), apparently not driven by the HLA-B27 allele (p=ns). Conclusion: We investigated for the first time the association between musculoskeletal manifestations of SpA and behaviour, localization, and extent of IBD. The combined peripheral-plus-axial joint involvement was more commonly associated with extensive colitis within UC-SpA. On the other side, patients with CD-SpA had more commonly an isolated axial involvement, when presenting with an intestinal stenosing phenotype and a colonic localization, and dactylitis, when showing a fistulizing behaviour and an ileo-colic involvement. Furthermore, uveitis was more commonly detected in CD-SpA with perianal disease. Profiling patients according to IBD characteristics might be useful in designing studies and tailored trials for IBD-SpA. REFERENCES: NIL . Acknowledgements: NIL . Disclosure of Interests: None declared . © The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.

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