ABSTRACT
Ankylosing spondylitis (AS), together with reactive arthritis (ReA), arthritis/spondylitis spectrum associated with psoriasis (Pso) and inflammatory bowel disease (IBD) and undifferentiated spondyloarthritides (uSpA) are part of the spondyloar-thritides (SpA). AS is the most frequent subtype of SpA followed by uSpA and psoriatic arthritis (PsA). The prevalence of the whole group of SpA has been recently estimated between 0.6% and 1.9% with an implicated AS prevalence between 0.1% and 1.1% (1–4). AS and PsA are regarded as the SpA subsets with the most severe course of disease.
