The objective is to compare the initial skin inflammatory transcriptomic profile of psoriatic patient responder to Adalimumab therapy (defined as the achievement of a Psoriasis Area and Severity Index 75 response at 16 weeks) with the transcriptomic profile of patient non-responder to Adalimumab therapy (defined as the non-achievement of a Psoriasis Area and Severity Index 50 response at 16 weeks) to identify differentially expressed genes in order to define predictive markers of response to the treatment.

Inclusion Criteria:

• Chronic plaque psoriasis involving at least 10% of body surface area, with a PASI score >10,
• Negative pregnancy test for women of childbearing potential, and use of an effective method of contraception,
• Pretreatment assessment to identify contraindications to anti-tumor necrosis factor-alpha therapy (chest x-ray and Intradermal reaction (detection of latent tuberculosis),
• Anti-tumor necrosis factor-alpha treatment with adalimumab has been prescribed

Exclusion Criteria:

• Classical exclusion criteria for adalimumab therapy (hypersensitivity to the product, severe heart failure, abscess, tuberculosis or other opportunistic infection),
• History of demyelinating disease, any unstable medical condition, patients with recurrent serious infections , history of cardiovascular or cerebrovascular disease , history of cancer
• Patients not having tuberculosis prophylaxis as per local guidelines for latent tuberculosis, or patients non-treated active tuberculosis
• Ongoing pregnancy or breastfeeding
• Absence of written consent,
• Prior treatment with one of the following anti-psoriatic treatments: biologics during the 3 months prior baseline visit, other systemic treatment during the 4 weeks prior baseline visit or topical therapy during the 2 weeks prior baseline visit.