- Patients with moderate to severe chronic plaque psoriasis with or without psoriatic arthritis AND who had started any first line of anti TNF alpha according to the labeling of these drugs BEFORE the study (i. e. the study will be restricted to anti TNF alpha naïve patients (first course). Patients who have been previously treated with any other non anti TNFA alpha biopharmaceutical (ustekinumab or anti IL17- secukinumab, ixekizumab, brodalumab) as a first line of biotherapy for psoriasis could be enrolled) after a wash out period of at least 5 half life time of the drug i.e. 16 weeks before inclusion