By Soehnchen Rolf, Soehnchen Carolina, Groene Dirk
PHOTODYNAMIC THERAPY IS a widely established treatment option in many dermatologic offices and hospitals. Initially only for treatment of cancerous lesion it is meanwhile used for a broader spectrum of medical as well aesthetic indications. However, photodynamic therapy (PDT) was introduced in dermatology on the quest to develop novel methods to treat diseases. The utilization of light as a trigger has fascinated many researchers and clinicians. The story began already in 1900 with the observation that certain protocol in the presence of the dye acridin and under the influence of light loose the capacity to migrate and replicate. Raab and Tappeiner in Munich termed their observation as “photodynamic effect”. 1904 the dermatologist Albert Jesionek, also in Munich, used this observation and applied it to clinical cases by treating patients with Lupus vulgaris and basal cell carcinomas with the photodynamic effect. Prior to this good effects of light exposure on lupus patients had been described by the danish dermatologist Niels R. Finsen, who was awarded with the Nobel price f medicine (1903) for this. Later Hans Fischer received the Noble Prize in 1930 for describing the porphyrin synthesis. The localisation of tumor cells by hematoporphyrin derivatives has been observed by Lipson which made modern photodetection possible. However, it needed until 1984 when Dougherty1 introduced porphyrins as photosensitizer on lung and bladder cancers, which meant to be the reawakening of this long time forgotten therapy. In 1999 aminolaevulinic acid solution received the approval by FDA2 for topical treatment of actinic keratosis. Photodynamic therapy involves administration of a tumor localizing photosensitizing agent (ALA, MAL) which is specifically absorbed and activated by light of a specific wavelength in diseased target cell or tissues. In the mitochondria a sequence of photochemical and photobiologic processes results in the generation of reactive oxygen species inducing necrosis and apoptosis in photodamaged skin.