High prevalence of ultrasonographic synovitis and enthesopathy in patients with psoriasis without psoriatic arthritis: a prospective case-control study.

OBJECTIVE: To investigate the presence of synovitis, tenosynovitis and enthesitis with power Doppler (PD) ultrasonography (US) in patients with psoriasis without musculoskeletal diseases as compared with controls with other skin diseases without musculoskeletal disorders. METHODS: A total of 162 patients with plaque psoriasis and 60 age-matched controls with other skin diseases, all without musculoskeletal diseases, were prospectively recruited at 14 centres. They underwent dermatological and rheumatological assessment and a blinded PDUS evaluation. Clinical assessment included demographics, comorbidities, severity of psoriasis, work and sport activities and musculoskeletal clinical examination. PDUS evaluation consisted of the detection of grey scale (GS) synovitis and synovial PD signal in 36 joints, GS tenosynovitis and tenosynovial PD signal at 22 sites, and GS enthesopathy and entheseal PD signal in 18 entheses. RESULTS: US synovitis and enthesopathy were significantly more frequent in psoriatic patients than in controls (P = 0.024 and 0.005, respectively). The percentage of joints with US synovitis was 3.2% in the psoriasis group and 1.3% in the control group (P < 0.0005). US enthesopathy was present in 11.6% of entheses in the psoriasis group and 5.3% of entheses in the control group (P < 0.0005). Entheseal PD signal was found in 10 (7.4%) psoriatic patients, whereas no controls showed this finding (P = 0.05). Among demographic and clinical data, having psoriasis was the only significant predictive variable of the presence of US synovitis [odds ratio (OR) 2.1; P = 0.007] and enthesopathy (OR 2.6; P = 0.027). CONCLUSION: Psoriatic patients showed a significant prevalence of asymptomatic US synovitis and enthesopathy, which may indicate a subclinical musculoskeletal involvement.