Psoriasis is a chronic immune mediated disease characterized by abnormal proliferation and differentiation of epidermal keratinocytes. It is a multifactorial disease with genetic background, environmental triggering factors, and immunological mediators, there are multiple clinical types of psoriasis the most common type is chronic plaque psoriasis (psoriasis vulgaris) which characterized by sharply demarcated scaly erythematous cutaneous lesions.
One of the most recent elements to be measured in psoriatic patients is the serum folate level, it is an essential water soluble vitamin naturally present in food that is required for biosynthesis of the DNA building units. Photolysis of folate may be significant, especially when serum is exposed in vitro to ultraviolet (UV) radiation, so the degradation effect of NB-UVB phototherapy in psoriatic patients is a matter of interest.
Narrowband ultraviolet B (NB-UVB) is an important therapeutic tool of generalized psoriasis. can be used as a single monotherapy or combined with other topical or systemic agents in more generalized severe psoriatic patients, inducing more apoptosis of pathogenic T cells and highly proliferating keratinocytes.