Background Enthesitis is considered a primary feature of psoriatic arthritis (PsA). PsA has a period of pre-clinical disease in which enthesitis can be detected in patients with psoriasis only by sensitive imaging modalities such as ultrasound. In this study we consider the presence of subclinical enthesitis detected by ultrasound in psoriasis patients as a proxy for PsA-risk.
Objectives We aimed to estimate the prevalence of subclinical enthesitis in patients with psoriasis without clinical arthritis and to assess their relation with known risk markers for PsA.
Methods 178 patients with a diagnosis of psoriasis confirmed by a dermatologist were enrolled. Patients with clinical signs suggestive of PsA were excluded. Information about demographics, co-morbid conditions and psoriasis phenotype was recorded. Musculoskeletal ultrasound assessment of 12 entheseal sites was performed according to a standard protocol. Enthesis thickness, structure, calcification/bone proliferation, erosion, bursa and power Doppler signal in the cortical bone profile, tendon and bursa were scored according to the MAdrid Sonographic Enthesitis Index (MASEI). A cut-off of ≥20 was used to define “subclinical enthesitis”. The association between the presence of subclinical enthesitis and patients' characteristics was assessed using logistic regression analysis adjusting for age.
Results A total of 19 of 178 patients (10.7%) were found to have subclinical enthesitis on ultrasound (MASEI≥20). The most frequently affected sites were the attachments of the distal patellar tendon (46.7%), Achilles tendon (44.1%) and plantar fascia (38%). 37 patients (20.8%) had one or more entheseal sites with positive power Doppler signal. Patients with subclinical enthesitis were more likely to be older (p=0.002), obese (p=0.01), diabetic (p=0.005), have nail pitting (p=0.006) and work in physically demanding occupations (p=0.01). Moreover, patients with subclinical enthesitis were more likely to report morning stiffness (p=0.008); however, no association was found with other musculoskeletal symptoms or patient reported outcomes estimating the degree of pain, function, fatigue and quality of life. On multivariate analysis the presence of ultrasonographic enthesitis was associated with obesity (Odds Ratio (OR) 14.3, 95% Confidence Interval (CI) 1.7, 118, p=0.01), current smoking (OR 5.1, 95% CI 1.3, 19.4, p=0.02), physically-demanding occupation (OR 4.3, 95% CI 1.3, 13.8, p=0.01), diabetes mellitus (OR 5.5, 95% CI, 1.1, 28.1, p=0.04) and psoriatic nail pitting (OR 4.3, 95% CI 1.5, 11.9, p=0.006).
Conclusions The presence of subclinical enthesitis is associated with known risk markers of PsA including: nail pitting, obesity and occupation-related mechanical stress. These findings reinforce the use of ultrasound for investigation of pre-clinical PsA in patients with psoriasis.
Disclosure of Interest None declared