Predominant ultrasonographic extracapsular changes in symptomatic psoriatic dactylitis: results from a multicenter cross-sectional study comparing symptomatic and asymptomatic hand dactylitis

Objective: Despite diffuse digital swelling, dactylitis may sometimes be asymptomatic. The objective of this study was to compare the clinical and ultrasonographic features of symptomatic with asymptomatic psoriatic arthritis (PsA) dactylitis. Methods: One hundred and twenty-five hand dactylitis were evaluated in a multicenter cross-sectional study for the presence of pain, subjective functional limitation, and tenderness (4-points scale) with the calculation of a Leeds Dactylitis Index (LDI) score. Fingers were subsequently investigated using high-frequency ultrasound (US) both in gray-scale (GS) and power Doppler (PD), for the presence and grading of flexor tenosynovitis, soft tissue edema, subcutaneous PD signal (PDUS), extensor tendon involvement, and joints synovitis. Clinical and US characteristics of symptomatic dactylitic fingers were compared with the asymptomatic dactylitic ones. Results: Symptomatic fingers (n = 80) had a significantly lower dactylitis duration compared to asymptomatic fingers (n = 36) (p < 0.001). Values of LDI, patient VAS-pain, and VAS-functional score were significantly higher in fingers with symptomatic dactylitis (p < 0.001 and p = 0.010, respectively). Symptomatic dactylitis had a higher prevalence of flexor tenosynovitis of grade > 2, soft tissue edema and subcutaneous PDUS signal (p < 0.001). Asymptomatic dactylitis showed a greater prevalence of joint synovitis (both in GS and in PD) than symptomatic dactylitis (p < 0.001). Conclusions: Digital tenderness and pain are linked to US tenosynovitis of grade > 2 and extra synovial abnormalities and conversely asymptomatic dactylitis is associated with joint-based synovitis.Key Points• Digital tenderness and local pain in psoriatic arthritis dactylitis are strongly associated with flexor tenosynovitis of grade> 2, soft tissue edema, and subcutaneous PD signal.• In psoriatic arthritis, asymptomatic dactylitis showed a greater prevalence of joint synovitis than symptomatic dactylitis.• In psoriatic arthritis, ultrasound inflammatory abnormalities are present in about 70% of cold dactylitis which is linked for disease chronicity.• In psoriatic arthritis, the flexor tendon and adjacent soft tissues play a significant role in symptomatic dactylitis.