Prevalence and clinical characteristics of psoriasis in spondyloarthritis: a descriptive analysis of 275 patients.

Objectives: To assess the prevalence of psoriasis among a cohort of patients with spondyloarthritis (SpA), to describe the clinical characteristics of psoriasis and associations with other manifestations.

Methods: This is a retrospective single-centre observational study. The patients were diagnosed with definite SpA (expert opinion), either axial or peripheral. Each patient underwent a direct interview by a physician. The data regarding history of psoriasis and its clinical characteristics were collected. Univariate and multivariate analyses of patients with versus without psoriasis were carried out.

Results: In all, 275 SpA patients were assessed: mean disease duration 16.7±11.8 years, 61.4% were men, 69.1% were diagnosed as axial SpA and 17.8% as peripheral SpA. In all, 84 patients (30.5%) had present or past psoriasis. The prevalence of psoriasis was high whatever the clinical presentation. Psoriasis was present before or concomitantly to diagnosis of SpA in 59/84 patients (70.2%). The most common types of psoriasis were plaque (66.7% of patients with psoriasis) and scalp psoriasis (65.5%). Other localisations were not rare, including palmoplantar pustulosis (20.2%) or nail psoriasis (19.1%). Patients with versus without psoriasis differed only through a lower proportion of radiological sacroiliitis (57.5% vs. 81.3 %, p<0.001).

Conclusions: With a prevalence of 30.5%, i.e. ten times higher than in the general population, this study confirms that psoriasis is a frequent and early manifestation in SpA and that a systematic search for psoriasis (e.g. scalp) is relevant in SpA for clinical practice, whatever the clinical presentation of SpA.