Characterisation of prodromal and very early psoriatic arthritis: a systematic literature review informing a EULAR taskforce

Background Identifying subjects at risk of imminent psoriatic arthritis (PsA) would allow these subjects to participate in therapeutic interventions to delay or prevent PsA development. Methods A systematic literature review (SLR) was conducted in 2021 in Medline, Embase, PubMed, Central databases and international congress abstracts (PROSPERO CRD42022255102). All articles reporting the characteristics of patients transitioning from psoriasis (PsO) to PsA and from undifferentiated arthritis (UA) to PsA were included. Clinical and imaging characteristics were collated before PsA onset and at time of PsA diagnosis. Results Eighteen of 23 576 references evaluated for PsO/PsA transition were analysed; 14 were cohort studies, 2 case-control studies. Two SLRs were used to enrich the project but were not analysed per se. Of 7873 references focusing on UA to PsA, 3 studies were included. Meta-analysis was not possible due to excessive data heterogeneity. Patients with PsO who developed PsA often reported joint pain, joint tenderness and functional limitations. Arthralgia (PsO, n=669; incident PsA, n=99) was associated with subsequent PsA development. On imaging, subclinical enthesopathy (PsO=325; Incident PsA=39) appeared linked to later PsA development. At the time of PsA onset (incident PsA, N=214), peripheral arthritis, mainly oligo-arthritis (ie, the mean number of swollen joints ranged from 1.5 to 3.2), was the most frequent pattern of clinical presentation. Conclusions Joint pain, arthralgia and entheseal involvement detected by imaging were frequent in individuals with PsO at risk for imminent PsA. Very early PsA was mainly oligoarticular. This review informed a EULAR taskforce on transition to PsA.