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Isolated axial disease in psoriatic arthritis and ankylosing spondylitis with psoriasis
  1. Timothy S H Kwok1,
  2. Mitchell Sutton2,
  3. Daniel Pereira2,
  4. Richard J Cook3,
  5. Vinod Chandran2,4,
  6. Nigil Haroon1,5,
  7. Robert D Inman1,6,
  8. Dafna D Gladman1,2
  1. 1Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  2. 2Centre for Prognosis Studies in the Rheumatic Diseases, Schroeder Arthritis Institute, University Health Network, Toronto, Ontario, Canada
  3. 3Statistics and Actuarial Science, University of Waterloo, Waterloo, Ontario, Canada
  4. 4Termerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  5. 5Schroeder Arthritis Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
  6. 6Schroeder Arthritis Institute, Toronto Western Hospital, Spondylitis Program, University Health Network, Toronto, Ontario, Canada
  1. Correspondence to Professor Dafna D Gladman, Temerty Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A1, Canada; dafna.gladman{at}utoronto.ca

Abstract

Objectives To compare isolated axial psoriatic arthritis (PsA), axial PsA with peripheral involvement and isolated axial ankylosing spondylitis (AS) with psoriasis. To evaluate predictors for developing peripheral disease from isolated axial PsA over time.

Methods Two PsA and AS cohorts identified patients with PsA with axial disease and isolated axial patients with AS with psoriasis. Logistic regression compared isolated axial PsA to axial PsA with peripheral involvement and isolated axial AS with psoriasis. Cox proportional hazards model evaluated predictors for developing peripheral disease from isolated axial PsA.

Results Of 1576 patients with PsA, 2.03% had isolated axial disease and 29.38% had axial and peripheral disease. human leucocyte antigen HLA-B*27 positivity (OR 25.00, 95% CI 3.03 to 206.11) and lower Health Assessment Questionnaire scores (OR 0.004, 95% CI 0.00 to 0.28) were associated with isolated axial disease. HLA-B*27 also predicted peripheral disease development over time (HR 7.54, 95% CI 1.79 to 31.77). Of 1688 patients with AS, 4.86% had isolated axial disease with psoriasis. Isolated axial patients with PsA were older at diagnosis (OR 1.06, 95% CI 1.01 to 1.13), more likely to have nail lesions (OR 12.37, 95% CI 2.22 to 69.07) and less likely to have inflammatory back pain (OR 0.12, 95% CI 0.02 to 0.61) compared with patients with isolated axial AS with psoriasis.

Conclusions Isolated axial PsA and AS with psoriasis are uncommon. HLA-B*27 positivity is associated with isolated axial PsA and may identify those who develop peripheral disease over time. Isolated axial PsA is associated with better functional status. Isolated axial PsA appears clinically distinct from isolated axial AS with psoriasis.

  • psoriatic arthritis
  • ankylosing spondylitis
  • inflammation
  • autoimmune diseases

Data availability statement

Data are available upon reasonable request. Data may be made available from the senior author upon request.

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Data availability statement

Data are available upon reasonable request. Data may be made available from the senior author upon request.

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Footnotes

  • Handling editor Josef S Smolen

  • Contributors TSHK, MS, RJC and D-DG were involved in study design. D-DG, VC, DP, NH and RDI were involved in patient recruitment. TSHK and MS were involved in data collection and analysis. TSHK prepared the initial draft and all authors were involved in reviewing the manuscript and providing critical comments.

  • Funding The University of Toronto Psoriatic Arthritis Program is supported by a grant from the Krembil Foundation.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.