A representative proinflammatory cytokine, IL-18, has been classified as a biomarker for the activity of psoriasis, in addition to other cytokines including transforming growth factor beta 1 (TGF-β1), tissue inhibitor of metalloproteinase 1 (TIMP-1), and matrix metalloproteinase 1 (MMP-1). This evidence concerns the gene TIMP1 and psoriasis.