Dysregulated Th17 cells and IL-17 synthesis in the skin, synovial space and endothelium promote synthesis of pro-inflammatory cytokines namely IL-1β, TNF and IL-6 and neutrophil chemoattractants such as IL-8, CCL20 and CCL2 as observed in psoriasis (Gaspari and Tyring, 2015; Silfvast-Kaiser et al., 2019) and psoriatic arthritis (Blauvelt and Chiricozzi, 2018; Pacha et al., 2020). This evidence concerns the gene IL17A and psoriatic arthritis.