Vitamin D3 in dermatology: a critical appraisal.

Vitamin D3 and its active metabolites can be generated within the skin. Their physiological activities encompass the regulation of calcium homeostasis, protooncogene expression and the production of a number of intracellular and secretory molecules from cells in various organs, including keratinocytes, fibroblasts and leukocytes. The major outcome of these activities is a decreased cellular proliferation and the modulation of inflammation and immunity, suggesting that these agents might be effective in the treatment of psoriasis, ichthyosis and allergic dermatitis. Several open and double-blind studies have indeed demonstrated some efficacy in psoriasis, but healing is slow and often incomplete. Higher doses are more effective but increase the potential of calcium deposition in the vascular tree and particularly the kidneys. Clinical results in ichthyosis and allergic dermatitis are disappointing. For the future, therapeutically more effective analogues of vitamin D3 with no calcium liability need to be developed.