Prevalence and Predictors of Subclinical Sonographic Enthesitis in Patients with Psoriasis: A Cross-sectional Study

Background: Enthesitis is characteristic of psoriatic arthritis (PsA), but subclinical sonographic enthesitis may exist with psoriasis (PsO) sans clinical arthritis, which can predispose to early development of PsA. Methods: In this cross-sectional study, consecutive adults with dermatologist-confirmed PsO, no clinical enthesitis or arthritis, and healthy controls (HCs) were recruited. Key exclusion criteria included active infection, recent trauma, high-intensity physical activity within 72 hours, and peripheral edema. Disease severity was assessed using the Psoriasis Area and Severity Index (PASI). Bilateral sonographic evaluation of four entheseal sites (lateral condyle of elbow, superior and inferior poles of patella, calcaneal insertion of Achilles tendons) was performed by a single-blinded operator using B-mode and power Doppler ultrasound. Enthesitis was defined per OMERACT ultrasound criteria. Results: Two hundred forty-six PsO patients (54.9% male; median age 38 years [IQR = 29–50]) and 50 HCs were enrolled. 53.5% of PsO patients had sonographic enthesitis (vs. 28% of HCs). The right patellar ligament was most frequently affected (12.6%). Among patients with enthesitis, the median disease duration was 14 months (IQR = 6–32), mean BMI was 22.8 ± 2.7 kg/m 2 , and median PASI was 7 (IQR = 3–13). Univariate analysis identified significant associations with nail involvement (OR = 4.12 [2.29–7.61]), dyslipidemia (OR = 3.28 [1.28–9.49]), hypertension (OR = 3.47 [1.36–10]), diabetes (OR = 2.93 [1.29–7.12]), the severity of PsO by PASI (OR = 1.06 [1.01–1.11]), and use of methotrexate (OR = 7.64 [3.04, 23.02]) and cyclosporin (OR = 3.3 [0.97–14.39]) with sonographic enthesitis. In multivariate analysis, nail involvement was a significant independent predictor (OR = 2.45, 95% CI = 1.28–4.68, P = .007). Conclusion: Sonographic subclinical enthesitis can exist in PsO patients without arthritis. Nail involvement and treatment with methotrexate independently predict its presence.