Photodynamic therapy and topical aminolevulinic acid: an overview

Photodynamic therapy is a non-invasive technique used in the treatment of skin diseases which has various advantages, one being the ability to localize treatment to the area being treated, which is common among most photosensitizers. Aminolevulinic acid is a prodrug that is metabolized intracellularly to form the photosensitizing molecule protoporphyrin IX (PpIX). When PpIX is activated by light, cytotoxic reactive oxygen species and free radicals are generated. This phototoxic effect may cause malignant and non-malignant hyperproliferative tissue to be destroyed, to decrease in size, and to eventually disappear. The application of topical aminolevulinic acid 20% followed by the use of a blue light photodynamic therapy illuminator is indicated in the US for the treatment of non-hyperkeratotic actinic keratoses of the face or scalp. There are data suggesting that aminolevulinic acid/photodynamic therapy may also be beneficial in acne vulgaris, verrucae, psoriasis, mycosis fungoides, and human papillomavirus. This treatment modality has also proven effective in the management of skin cancer such as, Bowen disease and basal cell carcinoma. Further experience in the use of photodynamic therapy will help define its utility in the management of actinic keratosis and other dermatoses.