ABSTRACT
Vitamin D, originally associated with rickets and osteomalacia, has recently been shown to have a role in a number of medical and dermatological diseases. It has been found that vitamin D receptors and the enzymatic machinery capable of converting circulating 25-hydroxyvitamin D [25(OH)D] to the active 1,25-hydroxyvitamin D [1,25(OH)D] is present in most cells in the body including the skin. It is well known that vitamin D analogs are effective in the treatment of psoriasis vulgaris because of their anti-proliferative and pro-differentiating effects on keratinocytes. However, new roles have been found for vitamin D in skin, such as immunomodulatory and anti-apoptotic effects thus raising a possibility of its use in conditions such as atopic dermatitis and infections. Increasing evidence now indicates that cutaneous vitamin D synthesis may help in prevention of skin malignancies and further, that cancer mortality may be reduced by oral supplementation of vitamin D. Various epidemiological studies have linked low levels of vitamin D to autoimmune diseases including vitiligo, and topical vitamin D has been used to treat vitiligo. This review focuses on a wide array of roles of vitamin D in various skin disorders with emphasis on both its well-established role as in psoriasis and the less characterized role in other disorders such as ichthyosis, tuberculosis or acne.