GÖTHA- The early arthritis and psoriasis study of Region Västra Götaland, Sweden - is a longitudinal observational study, which will prospectively and in parallel follow patients with newly diagnosed rheumatoid arthritis (RA, N=1000), psoriatic arthritis (PsA, N=500) and undifferentiated arthritis (N=100), together with patients with psoriasis (N=500). The study will also recruit healthy controls from the general population (N=3000).

The aims of the study are to define predictors for disease course and severity, treatment response, comorbidities, health related quality of life (HRQoL) and health economy.

The study is a collaboration between the department of Rheumatology and the department of Dermatology at Sahlgrenska University Hospital in Gothenburg, and the departments of Rheumatology at the hospitals of Alingsås, Borås, Uddevalla and Skövde, in the west of Sweden.

All patients with newly diagnosed RA, PsA and undifferentiated arthritis at the Rheumatology centers are eligible for inclusion. Patients with psoriasis will be recruited from the Department of dermatology at Sahlgrenska University Hospital.

The patients will be examined at baseline and at one, three, five and ten years. The assessments will include physical examination with evaluation of joints, entheses and skin and validated questionnaires regarding medical history, comorbidities, lifestyle, disease activity, bodily function, socioeconomic factors and HRQoL. Blood samples will be collected. The patients with arthritis will also undergo radiography of the lung, hands and feet, and Cone Beam Computed Tomography (CBCT) of hands and feet.

Inclusion Criteria:

• Patients with rheumatoid arthritis (RA) meeting the classification criteria of American College of Rheumatology (ACR) and/or European League Against Rheumatism (EULAR) från 2010
• Patients with psoriatic arthritis (PsA) meeting the classification criteria of Classification for Psoriatic Arthritis (CASPAR) PsA
• Patients with undifferentiated arthritis defined as a patients with a clear arthritis, but not meeting with established classifications criteria of any now known rheumatic disease
• Patients with psoriasis diagnosed at a dermatology department. The patients should not have any history of joint complaints with a duration of more than 6 weeks
• General population controls, matched for age, sex and residence of living to the included patients.

Exclusion Criteria:

• Inability to follow study protocol
• Swedish language difficulties
• Having other concomitant rheumatic diagnose (Sjögrens syndrome is not an exclusion criteria)

All patients at any of the involved rheumatology clinics with newly diagnosed RA, PsA or undifferentiated arthritis meeting the study criteria are eligible for inclusion.

Consecutive sampling

Patients with psoriasis diagnosed at a dermatology clinic. Consecutive sampling