The median values of TNF alpha, IL-17 and IL-23 in patients with psoriasis before phototherapy was significantly higher compared to the control group (10.45 pg/mL vs. 6.33 pg/mL, p = 0.003; 30.49 pg/mL vs. 14.65 pg/mL, p < 0.0001; 94.12 pg/mL vs. 64.41 pg/mL, p < 0.0001). Here, IL17A is linked to psoriasis.