The interleukin-17 pathway in psoriasis and psoriatic arthritis: disease pathogenesis and possibilities of treatment.

Psoriasis and psoriatic arthritis (PsA) are pathophysiological enigmas among rheumatic diseases. Substantial clinical advances have been made with new therapy targeting different components of the IL-17 and IL-23 pathways. At the same time, an increase in research on the topic has provided new insights into the potential functional effects of treatments on cell types, pathways, and tissues of interest. Here we review our knowledge of all IL-17 family members, their relationships with the IL-23 pathway, and the outcomes of relevant clinical trials in which different strategies for targeting these molecules have been tested in the treatment of moderate to severe psoriasis and PsA.