RT Journal Article SR Electronic T1 Relationship of Psoriatic Arthritis to Other Spondyloarthritides JF The Journal of Rheumatology JO J Rheumatol FD The Journal of Rheumatology SP 33 OP 35 DO 10.3899/jrheum.150632 VO 93 A1 Ignazio Olivieri A1 Salvatore D’Angelo A1 Michele Gilio A1 Carlo Palazzi A1 Ennio Lubrano A1 Angela Padula YR 2015 UL http://www.jrheum.org/content/93/33.abstract AB In the early 1970s, Moll and co-workers formulated the unified concept of spondyloarthritides, a group of conditions sharing similar clinical features. Subsequently, criteria for their classification have been proposed by Amor and coworkers, the European Spondylarthropathy Study Group, and the Assessment in SpondyloArthritis international Society. Opinion, however, is divided between those who believe that the different entities of the complex represent the variable expression of the same disease (“lumpers”) and those who think that these should be considered separately but under the same umbrella (“splitters”). Several sets of criteria have been proposed for psoriatic arthritis (PsA), the most recent being the ClASsification for Psoriatic Arthritis (CASPAR) criteria. According to some authors, there are persuasive arguments to support the view of PsA as a distinct entity.