Pathogenesis of psoriatic arthritis.

Psoriatic arthritis (PsA) is a heterogenous systemic inflammatory disorder which affects peripheral joints (PsA) and skin (psoriasis (Ps)), but also causes inflammation at entheseal sites, digits (dactylitis) and the axial skeleton. Over the past decade, there have been considerable advances both in our understanding of the pathogenesis of PsA and in the treatment of its diverse manifestations. This article reviews our current knowledge of the pathogenesis of PsA, and how genetic pre-disposition coupled with mechanical stress may influence the development of the pathognomonic features of PsA including enthesitis and osteoproliferation, with concomitant osteoporosis and erosive disease. We consider factors that influence the development of PsA in patients with Ps, and how improving our knowledge of the phenotypes of PsA may ultimately facilitate our goal of precision medicine, a key unmet need as defined by the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis.