Discovery of Arthritis in Psoriasis Patients for Early Rheumatological Referral

This is a monocenter cohort study, which will span at least 1 year from inclusion to follow-up. A sample of 300 patients known with PsC (cutaneous psoriasis) at the Department of Dermatology of the RadboudUMC, Nijmegen will be included. Inclusion of patients and collection of samples will be performed adjacent to their regular outpatient visits. During screening, patients will be assessed for signs and symptoms of PsA (psoriatic arthritis). This will include a 68 tender joint count (TJC) and 66 swollen joint count (SJC), a dactylitis count, the Leeds enthesis index (LEI) and a questionnaire screening for inflammatory back pain (IBP). At baseline visit, different parameters will be noted which can later be used to construct the prediction model. These will include sociodemographic data, relevant comorbidity, family history, characteristics of the PsC, intoxications, and constitutional and specific rheumatological signs and symptoms. During physical examination, the investigators will gather information about body measurements, skin and nail parameters, and rheumatological parameters. Also, a screening questionnaires already in use (PEST) will be used, as well as a quality of life scores (PsAID12, DLQI, Short-Form 12 Health Survey/SF-12). Blood will be drawn at baseline to check for different laboratory parameters which are associated with presence of PsA. Both inflammatory markers (e.g. cytokines, chemokines) as markers associated with bone metabolism are of interest. Also, DNA will be gathered via saliva and stored. At a later moment, this will be used to investigate the predictive value of different associated genetic polymorphisms and HLA-associations. If there is a clinical suspicion of PsA in the clinical exam, the patient will be referred to the Department of Rheumatology of the Sint Maartenskliniek, Nijmegen (SMK). From there on, they will be included in PsA regular care. After 1 year, patient files of the referred patients will be checked to confirm the diagnosis. Also, treatment changes and their effect will be noted. This will include both clinical parameters of the PsA and QoL. Patients already treated for PsA at a different clinic will not be referred to the SMK. They will be asked for permission to retrieve treatment-related data from their treating physician. Patients without musculoskeletal involvement will be re-evaluated after 1 year. Again, treatment changes and quality of life will be monitored.