title: Preface.
authors.affiliation: Oregon Health & Science University, Portland, OR, USA. Electronic address: deodhara@ohsu.edu.
authors.forename: Atul
authors.initials: A
authors.lastname: Deodhar
authors.affiliation: University of Ghent, Belgium.
authors.forename: Filip
authors.initials: F
authors.lastname: van den Bosch
mesh_terms: D015535:Arthritis, Psoriatic; D006801:Humans; D013167:Spondylitis, Ankylosing