ound: Psoriatic arthritis (PsA) phenotypes show different responses to the many available drugs. For a tailored medicine, it is important to choose the most effective treatment according to patients’ characteristics. Apremilast is recommended in PsA with moderate activity. In clinical practice, the most suitable PsA patients for apremilast are those affected by the peripheral oligoarticular arthritis. However, it is not so straightforward to definitely identify this phenotype. Musculoskeletal ultrasound (MUS) is a good tool for detecting the joints actually involved by PsA. The aim of this study is to verify if MUS assessment is useful in selecting the best PsA responders to apremilast. Methods: The following data of all consecutive PsA patients from 15 centres were recorded: anamnestic data, disease activity, PsA phenotype, apremilast treatment duration and reason of suspension. MUS assessment before apremilast treatment was the criteria which clustered patients in two groups. Apremilast retention rate estimate the drug’s effectiveness. The Cox analysis revealed the risk factors associated with treatment persistence. Mann-Whitney U and Chi-squared tests assessed the intergroup differences. Results: Only 40% of 356 patients (M:F: 152/204; median age 60 yrs) received MUS examination. In MUS group the moderate disease (median DAPSA 22.9 vs 26.9; p=0.0006) and the oligo-articular phenotype (63.6% vs 36.1%, p<0.0001) were more common. The retention rate was higher in MUS group (HR 0.55 IC95% 0.32-0.94; p=0.03). Conclusion: In apremilast treated PsA patients, baseline MUS assessment is related to an increased retention rate. MUS may identify patients’ characteristics favourable to apremilast response
