THE ACCUMULATION OF PROTOPORPHYRIN IX IN PLAQUE PSORIASIS AFTER TOPICAL APPLICATION OF 5-AMINOLEVULINIC ACID INDICATES A POTENTIAL FOR SUPERFICIAL PHOTODYNAMIC THERAPY

The success reported for the treatment of superficial skin carcinomas by photodynamic therapy with topical application of the photosensitize r precursor 5-aminolevulinic acid has therapeutic implications for the treatment of other skin disorders. This paper describes the accumulat ion of the photosensitizing agent protoporphyrin IX in areas of plaque psoriasis by monitoring of the fluorescence emission induced by low-i ntensity laser excitation at 488 mn, We present results from 15 patien ts with a total of 42 plaques and show that the characteristic fluores cence emission of protoporphyrin IX increases in intensity within the 6-h period following application of 5-aminolevulinic acid, suggesting that there is a potential for superficial photodynamic therapy. The ra te of increase and maximum intensity of fluorescence emission was not directly related to the applied quantity of the precursor, The variabi lity of the fluorescence intensity was as great between plaques at dif ferent sites on the same patient as between different patients. Also, the effect of plaque occlusion following application appeared insignif icant. Although there was only limited enhancement of emission from ar eas of skin surrounding the plaque, a significant build-up of sensitiz er was detected after several days in some areas of psoriasis that rec eived no application.