Subclinical Synovitis Among Patients With Psoriasis Without Musculoskeletal Involvement: A Systematic Review and Meta-Analysis.

Importance: Psoriasis affects up to 3% of the population, with 30% of patients with psoriasis developing psoriatic arthritis (PsA), yet the transition between psoriasis and PsA has yet to be fully understood. Subclinical synovitis is a hallmark of PsA and is thought to precede psoriatic arthritis; its detection among patients with psoriasis without musculoskeletal (MSK) involvement through medical imaging modalities could offer valuable insights into the transition from psoriasis to PsA.

Objective: To evaluate the prevalence of synovitis on ultrasonograms and magnetic resonance imaging (MRI) among patients with psoriasis without MSK involvement compared with healthy controls and patients with PsA.

Data sources: A comprehensive literature search was conducted in MEDLINE, Embase, Scopus, and Web of Science from inception to October 2024 using keywords related to psoriasis, synovitis, and medical imaging. A PROSPERO protocol was registered (CRD42024571308).

Study selection: Studies were eligible if they included patients with psoriasis without MSK involvement and assessed synovitis using imaging. Two reviewers independently screened studies and extracted data. Discrepancies were resolved by consensus. Twelve of 5132 initially identified studies met inclusion criteria.

Data extraction and synthesis: Data were extracted per PRISMA guidelines. Risk of bias was assessed using the Newcastle-Ottawa Scale. A random-effects model was used to pool risk ratios (RRs) for synovitis prevalence across comparison groups. Heterogeneity was assessed using the I2 statistic.

Main outcomes and measures: The primary outcome was the presence of imaging-detected synovitis among patients with psoriasis without MSK involvement compared with healthy controls and patients with PsA.

Results: Twelve studies (N = 2606 patients) were included comprising 1593 patients with psoriasis (mean [SD] age, 46.4 [7.5] years; 982 men [61.6%]), 327 patients with PsA (mean [SD] age, 50.2 [7.1] years; 210 men [64.2%]), and 686 healthy controls (mean [SD] age, 45.7 [6.9] years; 281 of 576 men [48.8%]). Synovitis was 2.5 times more likely among patients with psoriasis than controls (RR, 2.55; 95% CI, 1.18-5.52). Detection rates were higher with MRI (RR, 6.40; 95% CI, 1.87-21.95) than ultrasonography (RR, 2.50; 95% CI, 1.10-5.67). Synovitis was more frequent among patients with PsA than those with psoriasis, but the difference was not statistically significant (RR, 0.50; 95% CI, 0.13-1.87).

Conclusions and relevance: This systematic review and meta-analysis found that subclinical synovitis is significantly more prevalent among patients with psoriasis without MSK involvement compared with healthy controls. This finding suggests that imaging may aid in identifying individuals at risk for progression to psoriatic arthritis.