Subclinical enthesopathy of extensor digitorum tendon is highly prevalent and associated with clinical and ultrasound alterations of the adjacent fingernails in patients with psoriatic disease

Abstract Background Nail psoriasis disease is associated with an increased probability of psoriatic arthritis, and its clinical signs may have different correlates with the pathogenesis of adjacent bone destruction and have different prognostic value. Recent publications about psoriasis and nail psoriatic disease describe different ultrasonographic findings but the relationship between these ungueal alterations measured by ultrasonography and the presence of enthesopathy of the extensor digitorum has yet to be discovered. Objective To describe which ultrasonographic characteristics of nail psoriasis are associated with the presence of subclinical enthesopathy in patients with PsO and asymptomatic PsA. Methods Patients with psoriasis and asymptomatic psoriatic arthritis were included in the prospective study. Demographic, clinical data and PASI and NAPSI indexes were recorded of all the patients in the assessment visit. The US assessment included Achilles tendon, extensor digitorum tendon and US scan of the nail plate, nail matrix, nail bed and adjacent skin over nail matrix of the five nails of each hand. Results Forty‐eight patients were included in the study; 33 of them presented ultrasound evidence of extensor digitorum tendon enthesopathy. Nails of the patients with subclinical enthesopathy had a higher NAPSI and skin thickness than the nails of the patients without subclinical enthesopathy ( P = 0.047). Patients with asymptomatic enthesopathy had significantly thicker proximal nail folds (1.44 ± 0.312 vs. 1.23 ± 0.27, P = 0.023). Nail beds and matrices were also thicker but the differences were not statistically significant (1.77 ± 0.27 vs. 1.74 ± 0.21, P = 0.66, and 1.79 ± 0.28 vs. 1.67 ± 0.19, P = 0.10, respectively). No statistically significant differences in the trilaminar structure were found between both groups. Patients with and without asymptomatic enthesopathy of extensor digitorum tendons did not statistically differ as regards ultrasonographic alterations of the Achilles tendons (60.6% vs. 46.4%, P 0.368). Conclusion Enthesopathy abnormalities can be detected by US in patients with psoriasis without musculoskeletal complaints frequently. There is a close relationship between subclinical enthesopathy of the extensor digitorum tendon and the presence of nail alterations. Further studies are required to research what implications have the presence of these ungual alterations measured by US , and how it affects later development of a PsA.