Purpose of review: Psoriatic arthritis pathogenesis is incompletely understood and the pathophysiologic role of the synovium is only beginning to be elucidated. Currently, approaches similar to those applied to rheumatoid arthritis are being applied to psoriatic arthritis synovia.
Recent findings: Synovitis is being re-examined along with efforts to better characterize the clinical phenotype and improve patient stratification. The dermatological perspective brings an alternative view of autoimmunity and the role of innate immunity. A pathogenetic basis for the differing roles of skin and synovium is suggested by a landmark animal study that demonstrated a psoriasis-like skin disease coupled with a T cell and B cell dependent arthritis. The histopathology of the synovio-entheseal complex has been described. Systematic methods for evaluating synovitis have been developed and cross-sectional evaluations of psoriatic arthritis synovia in the context of other arthritides have been performed. Fresh looks at psoriatic arthritis synovia suggest similarity to rheumatoid arthritis synovia.
Summary: Research into the pathophysiology of psoriatic arthritis is at an early, yet promising stage. Instruments are being developed to characterize and stratify psoriatic arthritis. The role of synovia remains unclear, but we now have a better understanding of the pathology of innate and adaptive immunity and are reminded that psoriatic arthritis is a systemic disease.