This study will help researchers better understand the management of psoriatic arthritis (PsA). The goals of this study are a) to better understand how PsA responds to biologic therapy b) to build a registry of data and blood from patients with PsA for future studies and c) to figure out how to best measure disease activity and quality of life for those with PsA. To be eligible, patients must have a psoriatic arthritis and starting a TNFi (etanercept, adalimumab, infliximab, certolizumab, or golimumab). This study will last about 3 months and will include 2 study visits. The doctor will ask questions about your health, do a physical exam, and get a blood sample. Information from these activities will be entered into a scientific database. Information that could identify you will not be included.

You may be eligible for this study if you meet the following criteria:

• Conditions: Psoriatic arthritis
• Age: 18 years - 89 years
• Gender: All