Introduction: Biologic therapy has revolutionized treatment pathways in psoriatic joint and skin disease. It has also provided a useful tool with which pathological pathways of this condition may be explored.Areas covered: This review presents data on the clinical and biological effects of targeted therapy in psoriatic arthritis and psoriasis. Therapeutic agents covered include inhibitors of TNF, inhibitors of the IL-23/IL-17 axis and inhibitors of intracellular small molecules involved in the transduction of the inflammatory signal. Trial data on clinical and imaging efficacy is reviewed in parallel with studies on biological effects at tissue level. Pathological insights gained from the use of these treatments are explored.Expert commentary: A close relationship exists between specific pathological types and clinical manifestations of psoriatic disease, including responses to treatment. Studying these relationships is likely to improve understanding of disease and enable rational selection of specific treatments for patients with specific pathotypes.