Background/Purpose: To investigate the characteristics and differences of the ultrasonic imaging of enthesopathy in the lower extremity in patients with psoriatic arthritis(PsA), psoriasis(Ps) and other inflammatory arthritis, to explore the risk factors of Ps developing into PsA in the long term course, and to investigate the clinical practical value of the musculoskeletal ultrasound (MSUS) as a diagnostic modality in PsA.

Methods: Sex- and age-matched patients with 44 Ps, 44 PsA and 44 healthy controls (HCs) as well as 22 ankylosing spondylitis (AS), 22 rheumatoid arthritis (RA) and 11 osteoarthritis(OA) visting to the dermatological and rheumatic outpatient and ward department of the Chinese PLA general hospital were consecutively enrolled. MSUS of the lower limbs¡¯ entheses were performed, and then a comparation of ultrasonic imaging of enthesopathy between the 6 groups was made.

Results: 304(69.1%) of 440 enthesal sites were abnormal in Ps, compared with 345(78.4%) and 107(24.3%) abnormalities respectively in PsA and HCs (P=0.002, 0.000). The presence of erosion and power doppler (PD) signal in Achilles tendon were significantly higher in PsA than in Ps (9 vs 1, 12 vs 1, P=0.011, 0.002). Logistic regression results showed that a longer course of Ps may be a risk factor of developing into PsA (regression coefficient was 0.10, OR=1.10, P£¼0.001). The Glasgow Ultrasound Enthesitis Scoring System(GUESS) score was higher in PsA than in AS, RA and OA (P£¼0.001). The area under the ROC curve revealed that the GUESS accuracy in diagnosing PsA was 88.4 % with sensitivity and specificity of 86.4 and 79.8 %, respectively, at a cutoff value of 4.5.

Conclusion: The frequency of enthesopathy in the lower limbs was significantly higher in Ps and PsA who were absence of extremity musculoskeletal symptoms than HCs when detected by MSUS. Erosion and PD signal in Achilles tendon and a longer course of Ps may be the predictive factors of PsA. MSUS might help to identify entheseal changes in PsA.