Photodynamic therapy: a review of the literature and image documentation

Photodynamic therapy (PDT) consists of a chemical reaction activated by light energy that is used to selectively destroy tissue. The reaction requires a photosensitizer in the target tissue, a light source and oxygen. The most extensively studied photosensitizing agents for PDT are 5-aminolevulinic acid for the treatment of actinic keratosis and methyl-aminolevulinate, which has been approved for the treatment of actinic keratosis, basal cell carcinoma and Bowen's disease. The light sources used in photodynamic therapy should emit light at wavelengths within the absorption spectrum of the photosensitizer used in PDT treatment. Light emitting diode (LED) lamps are indicated for the photodynamic treatment of nonmelanoma skin cancer. PDT should be considered as a therapeutic option, particularly in the case of patients with superficial, multiple or disseminated lesions and for immunosuppressed patients. More recently, PDT has been indicated for a wide range of dermatological conditions such as photo-damaged skin, acne, hidradenitis, scleroderma, psoriasis, warts and leishmaniosis, among others. This article provides an extensive review of photodynamic therapy, its mechanisms, indications and results.