Combined Oral Vitamin D and UVB Versus UVB Alone in Treatment of Psoriasis Vulgaris

Psoriasis is a chronic immune-mediated inflammatory skin disease, with a prevalence of about 2%-3% in the general population. The primary manifestation of psoriasis most commonly manifests on the skin, although inflammatory processes can occur also in other organs . Vitamin D, also known as the sunshine vitamin, has long been known to be a hormone that regulates calcium-phosphorous homeostasis and safeguards the integrity of the skeletal system . The epidermis is the natural source of vitamin D synthesis by the action of ultraviolet light (UV) B of the sun or other UVB source . On the other hand, evidence is accumulating that vitamin D might represent a key modulator of immune and inflammation mechanisms . Recently, a role for vitamin D in the pathogenesis of different skin diseases, including psoriasis, has been reported. Psoriasis lesions are characterized by hyper-proliferation with incomplete differentiation of epidermal keratinocytes and decreased keratinocyte apoptosis, associated with inflammatory cellular infiltrate in both dermis and epidermis . Psoriasis Area and Severity Index (PASI) score is currently the preferred method for the assessment of the disease severity and extent . Physiologically, the active form of vitamin D and its receptor regulate the differentiation and proliferation of keratinocytes, the balance of the cutaneous immune system and the process of apoptosis. Several studies identified an association between polymorphisms of vitamin D receptor (VDR) and psoriasis susceptibility .The 1,25(OH)D has been shown to exert anti-proliferative effects on keratinocytes . The exact mechanism of action of NBUVB is not known. It is proposed that it acts in the following ways: (1) Cellular DNA is converted to pyrimidine dimers which interfere with cell cycle progression, (2) alteration in cytokine production, NBUVB phototherapy as the second-line treatment for psoriasis, recommended when the topical therapy fails, is contraindicated or impractical. UVB radia- tions of wavelength 311 nm may result in the clearance of disease symptoms after just 5-8 weeks.