TNF and psoriasis: Attenuation of CXCL10 levels is a consequence of therapies currently approved for the treatment of psoriasis and PsA, such as the phosphodiesterase-4 inhibitor apremilast [44] and the TNFα inhibitor etanercept [45, 46], further supporting a role for CXCL10 in the pathogenesis of PsA.