For systemic therapy, drugs such as NSAIDs are mainly used in psoriatic arthritis whereas non-biologic disease-modifying drugs (DMARDs, e.g. cyclosporine, methotrexate) and biologics (e.g. interleukin inhibitors, TNF inhibitors, phosphodiesterase inhibitors) are used for both psoriasis and psoriatic arthritis [38, 39, 45]. The gene discussed is TNF; the disease is psoriatic arthritis.