AB0927 CLINICAL AND RADIOGRAPHIC PHENOTYPE OF AXIAL PSORIATIC ARTHRITIS

Abstract

BackgroundThe latest data show that axial psoriatic arthritis (PsA) is less symptomatic, as compared with ankylosing spondylitis, and is associated with distinct radiographic features (1).ObjectivesTo analyze clinical characteristics of PsA patients (pts) with axial involvement, using data from a real-life outpatient cohort.Methods50 pts (M/F–30 /20) with PsA according to CASPAR criteria were included. All pts had either a present or past history of back pain, which rheumatologist suspected to be axial involvement. Pts’ age 42.0 [34.0; 54.0], disease duration 3.5 [0.3; 32.5] years. Pts underwent standard clinical examination of PsA activity: Ме BASDAI was 6.2 [3.8; 8.0], ASDAS-СRP 3.5 [2.5; 4.8], DAPSA 38,1 [20,2; 52,2], CRP 12.4 [0.3; 94.6] mg/L. All pts were evaluated for presence of inflammatory back pain (IBP) by ASAS criteria. HLA B27 antigen status was observed. Physical examination included Bath Ankylosing Spondylitis Metrology Index (BASMI). Pts underwent X-ray of sacroiliac joints (pelvic radiographs), cervical and lumbar spine, and hands and feet. Radiographic sacroiliitis (rSI) was defined as bilateral grade ≥ 2 or unilateral grade ≥ 3. All radiographs were interpreted by two experienced musculoskeletal radiologists. Me [Q25; Q75], Pierson-χ2 tests were performed. All p<0.05 were considered to indicate statistical significance.ResultsIBP was detected in 31 (62.0%) pts, while 19 (38.0%) pts didn’t meet IBP criteria – they had chronic back pain (CBP); 12 (24.0%) of all pts had episodic mild back pain. In 15 (30.0%) pts back pain started at age of above 40. RSI was found in 29 (58.0%) pts, while mostly symmetrical in 23/29 (79.3%) cases. Unilateral grade 2 sacroiliitis was found in 4 (8.0%) pts. 13/29 (44.8%) pts developed rSI without IBP. 38 (76%) pts had erosive arthritis, 18 (36%) pts had numerous erosions. HLA-В27 antigen was positive in 16 (32.0%) of pts. A correlation was revealed between the presence of rSI and limited spine mobility by BASMI (r=0.347). Association was found between rSI and numerous erosions (p=0.003), as well as between rSI and juxtaarticular new bone formation on hands and feet X-rays (р = 0.02). Syndesmophytes were found in 28 (56%) cases. 11 (22%) pts developed syndesmophytes without rSI. Asymmetrical syndesmophytes in the lumbar spine were found in 7/13 (53.8%) pts, vertebral non-bridging syndesmophytes in the lumbar and/or cervical spine in 16 (57.1%) pts. Restricted neck rotation was found in 85% of cases. Syndesmophytes in the cervical spine were found twice as often (26 pts) as in the lumbar spine (13 pts); 14 (28%) pts had isolated involvement of the cervical spine. An association was detected between asymmetrical syndesmophytes and radiographic changes on hands and feet X-rays such as osteolysis (р = 0.005) and juxtaarticular new bone formation (р = 0.05).ConclusionAxial PsA is often asymptomatic, one third of pts develop back pain at age above 40. HLA-B27 positivity was found in only 32% of pts. Pts with rSI are more likely to have severe peripheral arthritis with multiple joint erosions. Radiographic SI is associated with juxtaarticular new bone formation, which may indicate common mechanisms of bone formation in axial and peripheral skeleton. Syndesmophytes may occur in absence of sacroiliitis. Cervical spine involvement is more frequent in axial PsA pts. Asymmetrical syndesmophytes characteristic of PsA, are associated with typical, for PsA, radiographic changes on hands and feet X-rays, such as osteolysis and juxtaarticular new bone formation.