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Comparison of patients with axial PsA and patients with axSpA and concomitant psoriasis: an analysis of the German register RABBIT-SpA
  1. Anne Constanze Regierer1,
  2. Anja Weiß1,
  3. Fabian Proft2,
  4. Xenofon Baraliakos3,
  5. Frank Behrens4,
  6. Denis Poddubnyy1,2,
  7. Georg Schett5,
  8. Hanns-Martin Lorenz6,
  9. Matthias Worsch7 and
  10. Anja Strangfeld1,8
  1. 1Epidemiology Unit, German Rheumatism Research Center, Berlin, Germany
  2. 2Department of Gastroenterology, Infectiology and Rheumatology (Including Nutrition Medicine), Charité Universitätsmedizin, Berlin, Germany
  3. 3Rheumazentrum Ruhrgebiet, Ruhr University Bochum, Herne, Germany
  4. 4Institute for Translational Medicine & Pharmacology ITMP, Frankfurt am Main, Germany
  5. 5Department of Internal Medicine 3, University of Erlangen-Nuremberg, Erlangen, Germany
  6. 6Department of Internal Medicine V Hematology Oncology Rheumatology, Heidelberg University Hospital, Heidelberg, Germany
  7. 7Rheumatologist, Muehlhausen, Germany
  8. 8Department of Rheumatology and Clinical Immunology, Charité Universitätsmedizin, Berlin, Germany
  1. Correspondence to Dr Anne Constanze Regierer; Anne.Regierer{at}


Background Psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA) show certain overlaps: A subset of patients with PsA can develop axial involvement (axial PsA, axPsA), while a subset of patients with axSpA presents with psoriasis (axSpA+pso). Treatment strategy for axPsA is mostly based on axSpA evidence.

Objectives To compare demographic and disease-specific parameters of axPsA and axSpA+pso.

Methods RABBIT-SpA is a prospective longitudinal cohort study. AxPsA was defined based on (1) clinical judgement by rheumatologists; (2) imaging (sacroiliitis according to modified New York criteria in radiographs or signs of active inflammation in MRI or syndesmophytes/ankylosis in radiographs or signs of active inflammation in spine MRI). axSpA was stratified into axSpA+pso and axSpA without pso.

Results Psoriasis was documented in 181/1428 axSpA patients (13%). Of 1395 PsA patients, 359 (26%) showed axial involvement. 297 patients (21%) fulfilled the clinical definition and 196 (14%) the imaging definition of axial manifestation of PsA. AxSpA+pso differed from axPsA regardless whether clinical or imaging definition was used. axPsA patients were older, more often female and less often HLA-B27+. Peripheral manifestations were more often present in axPsA than in axSpA+pso, whereas uveitis and inflammatory bowel disease were more common in axSpA+pso. Burden of disease (patient global, pain, physician global) was similar among axPsA and axSpA+pso patients.

Conclusions AxPsA differs from axSpA+pso in its clinical manifestations, irrespective of whether axPsA is defined clinically or by imaging. These findings support the hypothesis that axSpA and PsA with axial involvement are distinct entities, so extrapolation of treatment data from randomised controlled trials in axSpA should be performed with caution.

  • psoriatic arthritis
  • spondylitis, ankylosing
  • epidemiology

Data availability statement

Data are available on reasonable request. Applications to access the data should be made to the corresponding author.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:

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Data availability statement

Data are available on reasonable request. Applications to access the data should be made to the corresponding author.

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  • Twitter @AnneRegierer, @ProftDr

  • Contributors ACR had full responsibility for the finished work and the conduct of the study, had access to the data, and controlled the decision to publish. ACR and AW had full access to all of the data in the study and were involved in analysis and interpretation of the data. ACR and AW took responsibility for the integrity of the data and the accuracy of the data analysis. ACR, AW, FP, XB, FB, DP, GS and AS were involved in study initiation, conception and design. All authors were involved in drafting the article and revising it critically for important intellectual content, and approved the final version to be published.

  • Funding RABBIT-SpA is supported by a joint, unconditional grant from AbbVie, Amgen, Biogen, Celltrion, Hexal, Janssen-Cilag, Lilly, MSD, Novartis, Pfizer, UCB and Viatris.

  • Competing interests None declared.

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

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.