IL17A and psoriatic arthritis: Interleukin-17 and IL-12 along with the TH1 cytokines (TNF-α, IL-1B, and IL-10) have been found in higher levels in psoriatic arthritis synovium and IL-17 and IL-23 have been implicated in the potentiation of osteoclastogenesis and bone erosion in psoriatic arthritis joints [26–28].