Subclinical synovitis and enthesitis in psoriasis patients and controls by ultrasonography in Saudi Arabia; incidence of psoriatic arthritis during two years.

Objective: To evaluate ultrasonographic subclinical inflammatory synovitis and enthesitis in psoriasis patients, without clinical arthritis or enthesitis compared with healthy controls, with a 2-year follow-up to study the associated incidence of psoriatic arthritis (PsA).

Methods: A total of 109 consecutive psoriasis vulgaris patients without clinical signs of PsA and 90 healthy controls were included from two tertiary medical centers. Subjects underwent dermatological examination, PASI score evaluation for severity of psoriasis, musculoskeletal examination using 68/66 joints count for tenderness and swollen joints. Patients were assessed for CRP, musculoskeletal ultrasound (MSUS) in the form of grayscale ultrasound (GSUS), and power Doppler ultrasound (PDUS) for eight entheses and 34 joints to detect MSUS subclinical enthesitis and synovitis. All patients were followed-up for 2 years to detect evolving PsA.

Results: Subclinical enthesitis and synovitis were detected in 39.5% of psoriasis patients and 10% of controls (P < 0.001). CRP was significantly higher in psoriasis patients with MSUS manifestations (P < 0.01). PDUS and GSUS subclinical synovitis and/or enthesitis were detected at least in one site in psoriatic patients more than in controls (P < 0.05). During a 2-year follow-up of patients, the annual PsA incidence was 4.3%. Psoriasis patients who developed PsA showed a higher prevalence of baseline enthesitis, higher PDUS and GSUS synovitis scores, and higher baseline CRP level than those who did not develop PsA.

Conclusions: MSUS subclinical synovitis and enthesitis are quite common in psoriasis patients. The incidence of PsA in Saudi's psoriasis patients was slightly higher than worldwide reports. Subclinical enthesitis, PDUS, and GSUS synovitis could predict PsA development.