IL23R and spondyloarthropathy: IL-23, as well as its effects on the production of other cytokines, is of particular significance in relation to both Ps and PsA because genomewide association studies have demonstrated that Ps is associated with polymorphisms in genes encoding both IL-23 subunits (p40 and p19) and the IL23R gene; the latter is also implicated in PsA and other forms of spondyloarthropathy [24,25].