Pos0525 Familial Clustering and B27 Positivity Indicate That Diffuse Idiopathic Skeletal Hyperostosis Is a Spondyloarthritis-Spectrum Condition: Results From a Clinical Study

Background: The classical risk factors for Diffuse Idiopathic Skeletal Hyperostosis (DISH) are diabetes, and metabolic syndrome 1. However, DISH has been found to coexist with spondyloarthritis (SpA) in reports and case series 2. Moreover, Psoriatic spondylitis syndesmophytes are similar to skeletal lesions of DISH 3. Despite these associations, and pathophysiologic similarities 4,5, DISH continues to be classified as an idiopathic, non-inflammatory disorder, with no reference to SpA in major texts and reviews 6. Objectives: To evaluate the prevalence of radiological features of DISH in SpA patients and the first-degree relatives of SpA patients wherever indicated. Methods: A retrospective study of SpA patients, presenting to the rheumatology out-patient at a tertiary care center in northern India, and to a peripheral clinic attached to it, were evaluated for radiological criteria for DISH 7 over one year (December 2022- December 2023). Wherever clinically indicated, consenting first-degree relatives (FDRs) who reported spinal symptoms or were already diagnosed with a spinal condition were screened radiologically for SpA/DISH and B27/Sacroiliitis. The presence of concomitant DISH radiology in SpA patients, familial clustering of SpA/DISH, presence of B27, and psoriatic arthritis (PsA) were noted. Results: Of the 248 patients with SpA, (including axial SpA and peripheral SpA/PsA patients), 89% were males, and the mean age of the patients was 37 years. After clinical evaluation and appropriate exclusions, the radiology and the HLAB27 status was assessed or the results were retrieved if done already. Patients who fulfilled the radiological features based on the DISH criteria (6) were also evaluated for SpA-related comorbidities and HLAB27 where indicated. The coexistence of SpA/DISH and other data related to DISH vis-a-vis SpA spectrum disorder was noted. Table 1 (A and B) lists the clinical features, radiology, and comorbidities of patients, either where family members of SpA have FDRs afflicted with DISH or vice-versa or single patients with DISH/SpA associated with other SpA comorbidities/HLA-B27. Conclusion: Familial clustering, radiological features consistent with PsA as well as axial-SpA, co-existence with SpA, B27 positivity, and uveitis, indicate that DISH is a SpA-spectrum condition. Larger multi-center studies may be required, and confirmation of this link may even allow therapeutic interventions on SpA lines for these patients. REFERENCES: 1 Vezyroglou G, Mitropoulos A, Antoniadis C. A metabolic syndrome in diffuse idiopathic skeletal hyperostosis. A controlled study. J Rheumatol. 1996 Apr;23(4):672-6. 2 Kuperus JS, Waalwijk JF, Regan EA, van der Horst-Bruinsma IE, Oner FC, de Jong PA, Verlaan JJ. Simultaneous occurrence of ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis: a systematic review. Rheumatology (Oxford). 2018 Dec 1;57(12):2120-2128. 3 Haddad A, Thavaneswaran A, Toloza S, Chandran V, Gladman DD. Diffuse idiopathic skeletal hyperostosis in psoriatic arthritis. J Rheumatol. 2013 Aug;40(8):1367-73. 4 Daoussis D, Liossis SN, Solomou EE, Tsanaktsi A, Bounia K, Karampetsou M, Yiannopoulos G, Andonopoulos AP. Evidence that Dkk-1 is dysfunctional in ankylosing spondylitis. Arthritis Rheum. 2010 Jan;62(1):150-8. 5 Senolt L, Hulejova H, Krystufkova O, Forejtova S, Andres Cerezo L, Gatterova J, Pavelka K, Vencovsky J. Low circulating Dickkopf-1 and its link with severity of spinal involvement in diffuse idiopathic skeletal hyperostosis. Ann Rheum Dis. 2012 Jan;71(1):71-4. 6 Reuven M. "Proliferative Bone Disease" Kelley 119(3):559-68. Acknowledgements: NIL. Disclosure of Interests: None declared.