Ustekinumab, an IL-12/23 antibody has been approved in the E.C. and U.S.A. for the treatment of moderate to severe psoriasis. The aim of this study is to determine in a randomized half-side comparison whether additional narrowband UVB-311nm phototherapy accelerates and improves the clearance of skin lesions in Ustekinumab-treated patients.

Patients with moderate to severe psoriasis who receive standard treatment with Ustekinumab (45 mg at week 0, 4, and every 12 weeks) are exposed to UVB-311nm phototherapy on a randomized body half (left or right; head exempt) 3 x per week for six weeks and/or until complete response (defined as reduction in PASI to < 3). PASI score, patient visual analogue score (VAS) for therapeutic response, and patient VAS for severity of skin lesions is assessed weekly; and at follow-up visits at month 3, 6, and 12. Paired Wilcoxon testing for differences in PASI and patient VAS scores is done; Fischer exact test is applied to determine differences in complete remission, PASI reduction > 90%, > 75% and/or 50% between body sites.

Inclusion Criteria:

• Age > 18 years
• Psoriasis patients who receive treatment with Ustekinumab

Exclusion Criteria:

• Age below 18 years
• Pregnancy or lactation
• History of malignant melanoma
• History of invasive squamous cell carcinoma of the skin
• Dysplastic melanocytic nevus syndrome
• Antinuclear antibodies (ds-DNA, Ro/SSA, La/SSB)
• Autoimmune disorders such as Lupus erythematosus or Dermatomyositis
• Photosensitive diseases such as porphyria, chronic actinic dermatitis, Xeroderma pigmentosum, basal cell nevus syndrome, and others
• General poor health status