Application of Ultrasound in the Assessment of Oligoarticular Psoriatic Arthritis Subset: Results from Patients Treated with Apremilast

Background Psoriatic arthritis (PsA) is an inflammatory rheumatic disease characterized by different phenotypes in terms of joint involvement. The so-called oligoarticular pattern involves fewer than five active joints at a different time points. The evaluation of disease activity in this subset of patients is an unmet need due to the lack of specific indices able to capture modifications over time. Objectives To evaluate the ability of musculoskeletal ultrasound to monitor the response to apremilast treatment in oligoarticular PsA patients. Methods We evaluated 24 oligoarticular patients (19 women, 5 men; median age 56 years, interquartile range (IQR) 19; median disease duration 5 years, IQR 5.75). All patients were assessed at baseline (T0), and after 6 (T1), 12 (T2), and 24 (T3) weeks. Clinical assessment included evaluation of 66 swollen joints and patient global health assessment. All the patients underwent ultrasound assessment of the clinically involved joints. Synovial effusion/hypertrophy and power Doppler were scored with a semi-quantitative scale (0-3). The total inflammatory score was the sum of the scores. Results We found a reduction in the ultrasound inflammatory score at all time points, with a significant improvement at 6 and 12 weeks of treatment compared with baseline: T0 median 8.5 (IQR 5.0); T1 3.5 (3.0); T2 2.0 (3.5); P = 0.01. We observed a significant reduction of patient global health assessment after 24 weeks (T0 median 50 (32.5); T3 40 (57.5); P = 0.01). Conclusions Musculoskeletal ultrasound could be useful in the assessment of treatment response in PsA patients with oligoarticular subset.