318 High prevalence of axial and peripheral spondyloarthritis features in patients with hidradenitis suppurativa

Background: Spondyloarthritis (SpA), a group of interrelated chronic auto-inflammatory rheumatic conditions, is reported to be more prevalent (2.3-28.2%) in hidradenitis suppurativa (HS) patients than in the general population. Identification of typical clinical SpA features may help to diagnose SpA. Objective: To investigate the prevalence of patient self-reported SpA clinical features in HS patients. Secondly, to identify patient characteristics associated with the presence of SpA features in HS. Methods: Cross-sectional study. A patient self-screening questionnaire concerning clinical axial and peripheral SpA entry criteria and additional SpA features, based on the Assessment in SpondyloArthrtis international Society (ASAS) definitions, was sent to all patients with a billing code of HS (between 2010- 2016) in two Dutch tertiary referral centers. Results: Analyzed were 47.2% (620/1313) questionnaires. Overall, 67.1% (n=416) patients reported ≥1 of the four ASAS entry classification criteria for SpA, of which 72.8% the axial SpA criterion (back pain ≥3 months and age of onset <45 years) and 27.2% peripheral SpA criteria (peripheral arthritis/enthesitis/dactylitis). Additionally, 87% of the 416 patients reported ≥1 additional SpA features. Compared to patients negative for SpA entry criteria (n=204), patients with self-reported SpA entry criteria were more frequently female (p<0.001), had a higher BMI (p<0.001), more often a positive smoking history (p=0.001), a longer HS disease duration (p=0.012), and showed more active HS symptoms at time of the survey response (p<0.001). Conclusion: Clinical axial and peripheral SpA features are very common in HS patients, especially in the classic HS patient (female, overweight, smoker), with active HS and a longer HS disease duration.