IL17A and psoriasis: The direct therapeutic targeting of TNF, IL-23, and IL-17 has proven to be clinically effective, albeit not without side effects and with an estimated rate of 50–70% of psoriatic patients who may show different response degrees to biologic drugs, reason why they are administered only in severe psoriasis cases and/or after developing psoriatic arthritis (occurring in 20/30% of cases after almost a decade from disease onset) [26,27].