Update on the epidemiology, risk factors, and disease outcomes of psoriatic arthritis.

Psoriatic arthritis (PsA) is a chronic inflammatory disease that affects different structures of the musculoskeletal system in addition to the skin and the nail. The complexity of the disease had been a barrier to understand the pathogenesis and define valid outcome tools; however, our understanding about the disease has considerably increased with time mainly because of the advances in imaging, new discoveries in genetics and underlying inflammatory pathways, and better understanding of the epidemiology of the disease and environmental risk factors. The purpose of this review is to summarize developments and changes in epidemiology, risk factors for developing PsA, and outcome measures with a focus on data obtained in the last 10 years.