Clinical Features of Psoriatic Arthritis: a Comprehensive Review of Unmet Clinical Needs.

Psoriatic arthritis (PsA) is a form of inflammatory arthritis (IA) affecting approximately 0.25% of the population. It is a heterogeneous disorder associated with joint damage, disability, disfiguring skin disease and in severe cases, premature mortality. Inherently irreversible and frequently progressive, the process of joint damage begins at, or before, the clinical onset of disease. Early recognition and intervention is thus crucial to patient outcome. At disease onset, however, PsA often resembles other forms of arthritis-especially rheumatoid arthritis (RA). Despite the similarities between PsA and RA, their distinctive pathologies require different treatments. For example, drugs that are effective in RA may not be effective in PsA and can even cause adverse effects. Since there is no currently validated test for PsA, the diagnosis is often missed or delayed and this has functional consequences for the patient. In the context of PsA and RA, making an accurate diagnosis is not the only challenge faced by rheumatologists. Choosing an effective and safe medication to manage the disease is another significant challenge and currently approximately 40% achieve meaningful responses such as minimal disease activity status. For the patient, several months may be lost as a result of trial and error testing-meanwhile, irreversible joint damage may occur. Clearly, more effective clinical tests are urgently needed to improve personalised patient care in PsA. Specifically, there is need to develop minimally invasive tests predictive of diagnosis, response to treatment and radiographic progression. In this review, we examined the biomarker development process, highlighted the importance of qualifying unmet clinical needs and emphasised the challenges that impede biomarker studies. We have compiled a comprehensive list of potentially clinically relevant biomarkers in PsA and provided a summary of proteomic technologies that might usefully support additional biomarker research in PsA.