Vitamin D and the Pathophysiology of Inflammatory Skin Diseases.

BACKGROUND: Vitamin D is a secosteroid, which was initially known for its skeletal role; however, in recent years, its functions in different organs have been increasingly recognized. In this review, we will provide an overview of vitamin D functions in the skin physiology with specific focus on its role in certain inflammatory skin conditions such as psoriasis and atopic dermatitis. METHODS: A comprehensive literature search was carried out in PubMed and Google Scholar databases using keywords like "vitamin D," "skin," "atopic dermatitis," and "psoriasis." Only articles published in English and related to the study topic were included in this review. RESULTS: Vitamin D is integrally connected to the skin for its synthesis, metabolism, and activity. It regulates many physiological processes in the skin ranging from cellular proliferation, differentiation, and apoptosis to barrier maintenance and immune functions. Vitamin D deficiency is associated with the risk of psoriasis and atopic dermatitis, and several clinical/observational studies have suggested the beneficial effect of vitamin D in the therapy of these 2 inflammatory skin disorders. CONCLUSIONS: Vitamin D exerts a pleiotropic effect in the skin and could be an important therapeutic option for psoriasis and atopic dermatitis.