Exploratory Study on Quality of Life in Patient With Moderate Psoriasis and Moderate Psoriatic Arthritis

This exploratory study will be used to identify questions that will be part of a new QoL questionnaire for patients with psoriasis and psoriatic arthritis and to determine the sample size needed for its validation. The new questionnaire will be a global QoL questionnaire which will take into account the impact of both psoriasis and psoriatic arthritis on QoL. STUDY OBJECTIVES * To evaluate the influence of psoriasis and psoriatic arthritis on patient's answers to QoL questions from DLQI, HAQ, EQ-5D, FACIT-fatigue and SF-36. * To identify an equal number of questions from DLQI, HAQ, EQ-5D, FACIT-fatigue and SF-36 where answers are mostly influenced either by psoriatic arthritis or by psoriasis.