Response to Upadacitinib of Enthesitis Evaluated by Ultrasound in Patients With Psoriatic Arthritis

Inclusion Criteria: * Adult male or female, at least ≥ 18 years old and ≤ 65 years old at Screening. * Clinical diagnosis of PsA with symptom onset at least 6 months prior to the Screening visit and fulfillment of the Classification Criteria for PsA (CASPAR) (19). * Physician decision on patient treatment with upadacitinib must have been reached prior to and independently of recruitment in the study. * Upadacitinib prescribed in accordance with the applicable approved label and local regulatory and reimbursement policies. * Inadequate response or intolerance to at least one bDMARD, one of them must be an anti-TNF according to the Spanish regulatory and reimbursement policies ("informe de posicionamiento terapéutico"). * Patients should have at least one ultrasound-determined peripheral enthesitis site according to OMERACT definition for ultrasound enthesitis. * Subjects must voluntarily sign and date an informed consent. Exclusion Criteria: * Patients who cannot be treated with upadacitinib according to the approved label (e.g., contraindications). * Consideration by the investigator, for any reason, that the subject is an unsuitable candidate to receive upadacitinib. * Unwillingness or inability to comply with the study requirements. * Prior exposure to any Janus kinase (JAK) inhibitor. * Patients taking ≥ 10 mg of prednisone or equivalent