RecruitingClinical trialCytokine Expression in Psoriasis Patients With and Without Joint InvolvementThe objective of the resarch is to study the cytokine profile of patients with psoriatic arthritis and psoriasis in order to better understand the pathophysiology of the disease and the contribution of cytokines to the presence or absence of joint involvement. This research will compare cytokines levels in sera, in PBMC culture after LPS or CD3/CD28 agonist antibodies, and in skin biopsy.