Psoriatic arthritis (PsA) is a complex inflammatory disease with heterogeneous clinical features, which complicates psoriasis in 30% of patients. PsA involves multiple tissues and clinical domains including skins and nails as well as arthritis, spondylitis, enthesitis, and dactylitis. Power Doppler (PD) ultrasonography (PDUS) is a sensitive non-invasive imaging technology used to assess disease activity and treatment response in PsA. This is a prospective, observational, open-label study to investigate disease activity, therapeutic response and bone destruction based on ultrasonography findings in patients with PsA.