DC-STAMP: Regulators of Osteoclastogenesis and Response Marker in PsA

The Investigators will examine if DC-STAMP can serve as an early marker of TNFi response in PsA. Identification of such a biomarker would permit rapid transition to a new agent, a major treatment advance. TNFi are the most effective therapies in PsA, however, methotrexate is frequently initiated early in the disease course based on its significantly lower cost. Unfortunately, the efficacy of MTX has not been supported in clinical trials and up to 40% of patients do not respond to TNFi therapy. Moreover, valid biomarkers to predict MTX or TNFi responses are currently unavailable. This study may also provide the first data on the comparative efficacy of MTX and TNFi using clinical, Ultrasound (US) and biomarker outcomes.