The search of the published data was performed on the EMBASE, EBSCO, and PubMed Databases, combining the following terms: “paradoxical psoriasis” or “TNF alpha-induced psoriasis”, “psoriasis under TNF inhibitors” or “paradoxical psoriasiform reactions” with “genetic polymorphisms” or “genetic risk” or “SNP” or “biomarkers” or “gene polymorphisms predictors” or “gene”, and “risk factors”. The gene discussed is TNF; the disease is psoriasis.