This observational and prospective study evaluated the clinical correlations of sonographic lesions in consecutive psoriatic arthritis (PsA) dactylitis cases. Eighty-three dactylitic digits were evaluated clinically and sonographically before treatment and at one-month (T1) and three-month (T3) follow-up. Clinical evaluation included the Leeds Dactylitis Index-basic (LDI-b) score and the visual analogue scales for pain (VAS-p) and functional impairment (VAS-FI). High-frequency ultrasound with grey scale (GS) and power Doppler (PD) assessed flexor tenosynovitis (FT), soft tissue oedema (STO), extensor tendon paratenonitis, and joint synovitis. There was a statistically significant correlation between the clinical parameters (VAS-p, VAS-FI, and LDI-b) and FT and STO at T1 and T3. We found statistically significant improvement in FT and STO for the cases with clinically meaningful treatment responses (p < 0.001). After a multiple conditional logistic regression analysis, the only variables that correlated with a T1 clinical response were the resolutions of PD FT (OR 15.66) and PD STO (OR 6.23), while the resolution of PD FT (OR 27.77) and of GS STO (OR 7.29) correlated with a T3 clinical response. The clinical improvements of active dactylitis are linked to the regression of sonographic evidence of extracapsular inflammation (particularly FT and STO).

Introduction: Dactylitis is a hallmark of psoriatic arthritis (PsA). While its assessment is clinical, recently musculoskeletal ultrasonography (MSUS) has been applied to its monitoring. However, the evidence on MSUS application for toe dactylitis is limited. The aim of this study is to characterize the ultrasonographic features of toe dactylitis in PsA. Method: Patients with PsA and painful toe dactylitis were retrospectively identified from clinical records. Demographic and clinical variables were analyzed. Ultrasound images of the affected toe, allowing the assessment of grey scale (GS) and power Doppler (PD) were collected, to evaluate tenosynovitis, soft tissue oedema (STO), synovitis of metatarsophalangeal (MTP), proximal and distal interphalangeal (PIP, DIP) joints (all graded 0–3), and peritendonitis (PTI) at the MTP and PIP (graded 0–1). Clinical and ultrasonographic features were analyzed through descriptive statistics. Results: The study included 26 patients (30 toes) of which 9 (34.5%) females, with mean (sd) age of 46.8 (11.73). All but one patient had an oligoarticular phenotype. Tenosynovitis was the most frequent lesion, with GS abnormalities in 27/30 toes (90%) and PD in 25/30 (83.3%). STO was common (GS in 28/30 (93.33%) toes and PD in 20/30 (66.66%)). Synovitis was less common (63.33%, 46.66% and 33.33% of MTPs, PIPs and DIPs, respectively), while PTI was uncommon, with no patient presenting with PD. Conclusions: Ultrasound showed different elementary lesions in toe dactylitis confirming the complexity of this manifestation also at foot. These findings represent a first step toward the development of further imaging studies assessing toe dactylitis in PsA. Key Points• Tenosynovitis and soft tissue oedema were the most common ultrasonographic elementary lesion in acute toe dactylitis in psoriatic arthritis.• Synovitis was less frequent and peritendonitis was very uncommon.• Musculoskeletal ultrasound confirms the presence of multiple lesions in painful toe dactylitis, confirming the complexity of this manifestation.

Although dactylitis is a well-recognized feature of several rheumatic diseases, it has never been reported in association with calcium pyrophosphate deposition (CPPD) disease arthritis. This report describes two elderly women with CPPD-induced acute dactylitis mimicking inflammatory joint disease on clinical and ultrasound examination.

Review; Authors: N. Possemato, A. Rai, M. Oliva, N. Girolimetto, C. Salvarani, A. Marchesoni

Background: In psoriatic arthritis (PsA), clinical tenderness and ultrasound (US) capture distinct yet related aspects of entheseal disease activity. However, their longitudinal relationship after initiation of biologic disease-modifying antirheumatic drugs (bDMARDs), and the clinical significance of early discordance during follow-up remain unclear. Methods: In this retrospective observational cohort study based on routinely collected medical records, patients with CASPAR-defined PsA and clinically and ultrasonographically active enthesitis at baseline (Clin+/US+) who initiated bDMARD therapy underwent paired, same-day, blinded clinical and US assessments at approximately 6 and 12 months. Agreement between clinical and US findings was quantified using Cohen’s kappa. Discordant states (Clin−/US+ and Clin+/US−) were prespecified, and predictors of Clin−/US+ status at 6 months were analyzed using models that accounted for within-patient clustering. Results: Thirty-nine patients contributed 82 entheses and were treated with either tumour necrosis factor inhibitors (53.8%) or interleukin-17 inhibitors (46.2%). At 6 months, agreement between clinical and US assessments was fair (κ = 0.286; 95% confidence interval [CI], 0.080 to 0.492), with 23.2% of entheses classified as Clin−/US+ and 52.4% as concordantly inactive. At 12 months, agreement improved to substantial-to-almost-perfect levels (κ = 0.779; 95% CI, 0.595 to 0.963), with only 1.2% of entheses remaining Clin−/US+ and 80.5% achieving concordant remission. NSAID exposure was the only significant predictor of Clin−/US+ status at 6 months in univariable analysis (odds ratio [OR], 3.82; 95% CI, 1.27 to 11.47; p = 0.017) and remained associated after multivariable adjustment (OR, 6.16; 95% CI, 1.14 to 33.2; p = 0.03). Conclusions: In PsA patients starting bDMARD therapy, clinical and US assessments of enthesitis showed partial discordance at 6 months, followed by greater convergence at 12 months. These findings suggest that clinical and imaging abnormalities may resolve asynchronously during follow-up and should therefore be interpreted in an integrated, time-aware manner. Residual US abnormalities in the setting of clinical improvement should be interpreted cautiously and within the broader clinical context.