However, the pro-inflammatory qualities of these cytokines have made them important in the pathology of several chronic autoimmune and fibrotic inflammatory diseases (Miossec and Kolls, 2012), including psoriatic arthritis and ankylosing spondylitis, in which antibodies against IL-17A have revolutionised disease treatment (Boyd and Kavanaugh, 2015; Baraliakos et al., 2017). This evidence concerns the gene IL17A and psoriatic arthritis.