Is axial psoriatic arthritis distinct from ankylosing spondylitis with and without concomitant psoriasis?
OBJECTIVE
The aim of this study was to compare patients with ankylosing spondylitis with psoriasis (ASP) and without psoriasis (AS), to axial PsA (axPsA) patients.


METHODS
Two adult cohorts were recruited from the AS clinic: ASP and AS. These two cohorts were compared with two adult cohorts recruited from the PsA clinic: axPsA (radiographic sacroiliitis: ⩾bilateral grade 2 or unilateral grade 3 or 4); and Peripheral PsA. All patients were followed prospectively according to the same protocol. The demographic, clinical and radiographic variables were compared. Adjusted means were used to account for varying intervals between visits. A logistic regression was performed and adjusted for follow-up duration.


RESULTS
There were 477 axPsA patients, 826 peripheral PsA, 675 AS and 91 ASP patients included. AS patients were younger (P < 0.001), more male and HLA-B*27 positive (76%, 72% vs 64%, P ⩽ 0.001, 82%, 75%, vs 19%, P = 0.001). They had more back pain at presentation (90%, 92% vs 19%, P = 0.001), worse axial disease activity scores (bath ankylosing spondylitis disease activity index: 4.1, 3.9 vs 3.5 P = 0.017), worse back metrology (bath ankylosing spondylitis metrology index: 2.9, 2.2 vs 1.8, P < 0.001), worse physician global assessments (2.4, 2.2 vs 2.1, P < 0.001), were treated more with biologics (29%, 21% vs 7%, P = 0.001) and had a higher grade of sacroiliitis (90%, 84% vs 51%, P < 0.001). Similar differences were detected in the comparison of ASP to axPsA and in a regression model.


CONCLUSION
AS patients, with or without psoriasis, seem to be different demographically, genetically, clinically and radiographically from axPsA patients. axPsA seems to be a distinct entity.
['Feld|Joy|J|', 'Ye|Justine Yang|JY|', 'Chandran|Vinod|V|', 'Inman|Robert D|RD|', 'Haroon|Nigil|N|', 'Cook|Richard|R|', 'Gladman|Dafna D|DD|']
D000328:Adult D015535:Arthritis, Psoriatic D003937:Diagnosis, Differential D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D011565:Psoriasis D012189:Retrospective Studies D012720:Severity of Illness Index D013167:Spondylitis, Ankylosing D055815:Young Adult
axial psoriatic arthritis ankylosing spondylitis