The aims of this study are to find a correlation between levels of inflammatory cytokines such as TNF-α, IL-23, IL-17A, and IL-17F and disease duration and severity scores in psoriasis; to test if the decrease in any of the aforementioned cytokines is correlated with an amelioration in disease severity scores; and to analyze if any of the four biologic agents used are linked with a greater decrease in overall cytokine levels. The gene discussed is IL17A; the disease is psoriasis.