A Study of Guselkumab and Interleukin-17 (IL-17) Inhibitor Therapies in Participants With Psoriatic Arthritis in Routine Clinical Practice

Inclusion Criteria: Main study: * Have a confirmed diagnosis of PsA as determined by a rheumatologist with reference to Classification criteria for Psoriatic Arthritis (CASPAR) * Start guselkumab or any approved interleukin-17 inhibitor (IL-17i) as a first, second, third, or fourth line of biologic disease-modifying antirheumatic drugs (bDMARD) therapy for the indication of PsA as part of standard clinical practice (according to local label, local regulations, and/or reimbursement requirements) at the time of enrollment into the observational study or within a maximum of 2 months after the initial baseline visit or after repeated baseline data collection * Sign a participation agreement/Informed consent form (ICF) allowing data collection and source data verification in accordance with local requirements * Able to read, understand, and intend to comply with completion of all Electronic patient-reported outcome (ePRO) instruments * The treatment decision must be taken by the participating rheumatologist prior to, and independently of the participant's inclusion into the study, following clinical practice in accordance with local and overarching guidelines and local regulations Substudy: * Must sign the substudy ICF allowing data collection in accordance with local requirements * Is scheduled to receive guselkumab or IL-17i, per routine clinical practice, in the main study * Currently using or is willing to use wearables and/or commercial applications to track their disease within the course of their normal daily activities Exclusion Criteria: Main study: * Start guselkumab or an IL-17i therapy as fifth or further line of biologic treatment * Have already taken a specific IL-17i or IL-23i treatment and are planning on re-taking that specific treatment again * Unwilling or unable to participate in long-term data collection * Received an investigational drug (including investigational vaccines) or used an invasive investigational medical device within 30 days before the start of the study (that is, signing of informed consent) * Currently enrolled in any interventional study or any Janssen-sponsored observational clinical study (contemporary participation into observational studies or registries not sponsored by Janssen is acceptable) Substudy: * Have an insufficient command of language to interact effectively with the smartphone application, in the opinion of the investigator at each site * Any condition for which, in the opinion of the investigator, participation would not be in the best interest of the patient (example, compromise the well-being) or that could prevent, limit, or confound assessment * Unwilling or unable to comply with substudy assessments