Psoriasis is mainly mediated by the effector cytokines secreted from Th17 cells, which activate the STAT3 signaling in keratinocytes, thereby inducing their hyper-proliferation and the expression of pro-inflammatory cytokines, growth factors, anti-microbial peptides and matrix metalloproteinases that cause chronic inflammation [6,33]. This evidence concerns the gene STAT3 and psoriasis.