AB0840 INFLUENCE OF PSORIATIC ARTHRITIS (PsA) ON BONE LOSS AND ANALYSIS BETWEEN AXIAL AND PERIPHERAL PsA IN JAPANESE PATIENTS

Background: Osteoporosis is one of the major comorbidities in patients with psoriasis and psoriatic arthritis (PsA). It has been reported that PsA induces fragility bone structure1 and high risk of osteoporosis2. However, there is no report about relationship between psoriatic arthritis and osteoporosis in Japanese patients and its mechanism has not been elucidated. Objectives: The objective of this study is to investigate influence of PsA on bone mineral density (BMD) and its mechanism including analysis between axial and peripheral PsA in Japanese patients. Methods: This study was retrospective study. We examined 58 cases of PsA and 29 cases of RA that underwent DXA tests at our facility from January 2017 to July 2019 (Table 1). The axial PsA was classified as axial SpA using the ASAS classification criteria. First, we investigated influence of PsA containing both axial (n=30,19 males, 11 females, mean age: 50.6 years) and peripheral (n=28, 19 males, 9 females, mean age: 58.0 years) subtypes on BMD measured by dual-energy X-ray absorptiometry. Second, we measured serum bone metabolism markers (P1NP: type I procollagen-N-propeptide, TRACP-5b: tartrate-resistant acid phosphatase 5b) and bone remodeling effector molecules (Dkk1: Dickkopf1, sclerostin, 25(OH)D: 25-hydroxyvitamin D) to elucidate differences in BMD between axial and peripheral PsA. Furthermore, rheumatoid arthritis (RA) (n=29, 2 males, 27 females, mean age: 66.2 years), as a reference disease, was also evaluated for comparison with axial and peripheral PsA. Osteoporosis and Osteopenia were defined as T-score ≤ -2.5 or %YAM ≤70%., -1.0 -2.5 or 80>%YAM >70% respectively. Results: 58 patients with PsA indicated low T-score, Z-score and %YAM in both lumbar spine and proximal femur (Table 1). Axial PsA and peripheral PsA showed osteoporosis in 16.7% and 35.7%, and osteopenia in 20.0% and 32.1%, respectively, despite the fact that there were many middle-aged men. Comparison between axial and peripheral PsA, axial PsA showed higher BMDthan peripheral PsA. In bone remodeling makers, P1NP in both PsA were almost same, but TRACP-5b, bone resorption marker, in axial PsA was lower than that in peripheral PsA(Table 2). In bone remodeling influencer molecules, Dkk1, and sclerostin in axial PsA was slightly higher than those in peripheral PsA, whereas 25(OH)D is almost same as the both PsA. On the other hand, RA also indicated low T-score and %YAM in both lumbar spine. P1NP in RA showed slightly lower, but TRACP-5b and Homocysteine in RA higher than those in axial and peripheral PsA. Dkk1 and sclerostin in RA were slightly lower than those in both PsA. Conclusion: Peripheral PsA indicated more severe bone loss than axial PsA in our study. There were some differences in bone remodeling markers and bone remodeling effector molecules between axial and peripheral PsA, but the relationships between BMD and these parameters were not confirmed. Further studies are needed to elucidate bone loss mechanism in these PsA. References: [1]Zhu TY, et al. Osteoporosis Int. 2015; 26:261–272. [2]Kathuria R, et al. J Am Acad Dermatol. 2017;76:1045-53. Disclosure of Interests: Shigeyoshi Tsuji Grant/research support from: Eli Lilly, Speakers bureau: AbbVie, Asahi Kasei, Chugai, Daiichi Sankyo, Eli Lilly, Eisai, Mitsubishi Tanabe, Celgene, and Novartis Pharma K.K., Tetsuya Tomita Consultant of: Eli Lilly and Company, Mari Higashiyama: None declared, Takaaki Noguchi: None declared, Toshikazu Mouri: None declared, Jun Hashimoto Speakers bureau: AbbVie, Asahi Kasei, Chugai, Daiichi Sankyo, Eli Lilly, Eisai, Mitsubishi Tanabe, Celgene, and Novartis Pharma K.K.