In addition, robust evidence implicates IL-17A (either independently or synergistically with other pro-inflammatory mediators [4, 5]) to have a pivotal function in the pathogenesis of immune-mediated inflammatory diseases such as psoriasis, psoriatic arthritis (PsA), and axial spondyloarthritis for which IL-17A is now a therapeutic target [6, 7]. This evidence concerns the gene IL17A and psoriatic arthritis.