Improved Response of Plaque Psoriasis after Multiple Treatments with Topical 5-Aminolaevulinic Acid Photodynamic Therapy

Abstract

We investigated the clinical response of 10 patients with plaque psoriasis to multiple treatments with photodynamic therapy, using topical application of 5-aminolaevulinic acid followed by exposure to broad-band visible radiation. Treatment was performed up to 3 times per week, with a maximum of 12 treatments, using a light dose of 8 Jcm(-2) delivered at a dose-rate of 15 mW cm(-2). Eight patients showed a clinical response. Out of 19 treated sites, 4 cleared, 10 responded but did not clear and 5 showed no improvement. Of the 4 sites that cleared only 1 did so fully, after 7 treatments, 45 days after the start of therapy. Of the 10 sites that responded partially, the greatest reduction in scale, erythema and induration index occurred after a minimum of 3 and a maximum of 8 treatments. The intensity of 5-aminolaevulinic acid-induced protoporphyrin IX fluorescence, recorded prior to the first treatment, varied between sites on the same patient as well as between patients. There was also a variation in fluorescence intensity recorded from the same site immediately prior to subsequent treatments, although the pretreatment levels generally decreased as the study progressed and then increased as psoriasis relapsed. Biopsies confirmed that fluorescence was localized throughout the epidermis and stratum corneum, but the level was not consistent between sections taken within the same biopsy. We also observed fluorescence at sites distant from the ones that received 5-aminolaevulinic acid, which was not present prior to the start of the treatment programme, but found no evidence of elevated levels of plasma porphyrins. The level of discomfort associated with this therapy increased with increasing values of the calculated photodynamic dose, defined as the product of the initial photosensitizer concentration and the percentage reduction in fluorescence following irradiation. Therefore, although clinical efficacy improved with multiple treatments, unpredictable response and patient discomfort make ALA-PDT unsuitable for the treatment of psoriasis.

Photodynamic antimicrobial chemotherapy using zinc phthalocyanine derivatives in treatment of bacterial skin infection

“…The other advantage is that repeated photosensitization of bacterial cells does not induce a selection of resistant strains. 10 Although PACT is gaining increasing acceptance for the treatment of locally occurring infections such as psoriasis 11 and scleroderma 12 in dermatology, it is not, at present, a mainstream therapeutic option.…”

A Critical Reappraisal of Off-Label Use of Photodynamic Therapy for the Treatment of Non-Neoplastic Skin Conditions

“…Indeed, immunohistochemical investigations of psoriatic lesions treated with PDT showed normalization of epidermal proliferation and differentiation, decreased infiltration of pathogenetically relevant T-cell subsets [59], and reduced dermal neovascularization [60]. However, clinical results have been disappointing with limited and unpredictable clinical response and significant pain, stinging, and burning during and after irradiation is frequent [60-64]. In addition, costs could most often be excessive because psoriatic lesions may cover a large part of the body surface and clearing of lesions, if any, is seen after repeated treatments.…”