PHOTODERMATOLOGY: CURRENT PRINCIPLES AND PRACTICE
Vol. 30. No. 4
Knowledge of light-skin interactions remains a critical aspect of dermatology. During the past decade, advances have been made with the use of light-based technologies in the diagnosis and management of skin disease. Changes in demographics within the United States and other western countries have highlighted the need for a better understanding of photobiology in skin of color. The increase in skin cancer incidence, including melanoma, continues to challenge us to come up with more optimal photoprotective measures. This issue of Seminars in Cutaneous Medicine and Surgery is devoted to current principles and practice in photodermatology. The goal is to provide a snapshot of up-to-date information on disorders, therapies, and pathophysiologic mechanisms influenced by ultraviolet and visible light. Basic science data are incorporated with practical clinical approaches, resulting in a meaningful and relevant discussion of key topics in photodermatology.
Phototherapy has proven to be one of the most versatile and effective treatment options for a variety of inflammatory and pigmentary skin diseases. However, the use of these treatment modalities in patients of color requires some special considerations. The modality chosen, the dosing of the treatment and duration of treatment are all issues to be considered for patients of color treated with ultraviolet phototherapy. In addition, there are some diseases which are more commonly seen in patients of color. These diseases may have better treatment outcomes using newer phototherapeutic options such as the long pulsed Nd:YAG laser or UVA1. As our population in the United States becomes more diverse it would behoove all dermatologists to acquaint themselves with the special circumstances of treating ethnic patients with phototherapy. Semin Cutan Med Surg 30:184-189 © 2011 Elsevier Inc. All rights reserved.MORE
Dermatologists are presented with a diversity of therapeutic modalities for the treatment of inflammatory, sclerosing, and neoplastic conditions, but with the development of various new irradiation devices that utilize specific parts of the electromagnetic spectrum, phototherapy has become a more viable, accessible, and efficacious option in the treatment of these conditions. The ultraviolet (UV) range (10-400 nm) is further subdivided into UVA and UVB, each of which has been particularly useful in a number of skin conditions. The most commonly used forms of UV irradiation are UVA1, psoralen plus UVA (PUVA), and narrowband (NB) UVB. Each of these modalities differ in their mechanism of action, indications, and side effect profiles, and it is important that clinicians be familiar with these differences. Today, phototherapy is a valuable option in the treatment of many nonpsoriatic conditions including atopic dermatitis, sclerosing skin conditions such as morphea, vitiligo, and mycosis fungoides. Due to its relative safety, phototherapy may be used in most populations, including children and pregnant women. However, contraindications and side effects are known and should be considered before patients begin a phototherapeutic regimen.MORE
Photodynamic therapy (PDT) involves the activation of a photosensitizing drug, which preferentially localizes to diseased skin, by irradiation with light to cause selective cytotoxic damage. Since its discovery in the early 20th century and the development of topical photosensitizers 2 decades ago, PDT is increasingly being used in dermatology for a wide range of neoplastic, inflammatory, and infectious cutaneous conditions. Topical 5-aminolevulinic acid and methyl aminolevulinic acid, the most commonly used agents in PDT, have received Food and Drug Administration approval for the treatment of actinic keratoses, and many second-generation photosensitizers are under investigation. Compared with conventional therapies, PDT has the advantage of being noninvasive and capable of field treatment. It is also associated with quicker recovery periods and excellent cosmetic results. Because of these benefits, PDT is being evaluated as a potential treatment option for many dermatologic conditions and has been shown to be effective for certain nonmelanoma skin cancers. Although research is still limited, PDT might also have a therapeutic benefit for cutaneous T-cell lymphoma, acne, psoriasis, leishmaniasis, and warts, among others. This article is a review of the clinical applications of PDT in dermatology and summarizes the current evidence in literature describing its efficacy, safety, and cosmetic outcome. Semin Cutan Med Surg 30:199-209 Published by Elsevier Inc.MORE
Commercial sunscreen based on nano-sized titanium dioxide (TiO2) and zinc oxide (ZnO) delivers superior UV protection and reduces whitening on skin compared to the older generations of inorganic sunscreens. This review discusses the historical use of nano-sized TiO2 and ZnO in sunscreen and the relationship between UV attenuation and the primary particles, aggregates and agglomerates that make up these inorganic oxides. In addition we reviewed the recent safety concerns surrounding these materials, specifically, percutaneous penetration of TiO2 and ZnO nanoparticles through human skin and their potential to cause phototoxicity. Semin Cutan Med Surg 30:210-213 © 2011 Elsevier Inc. All rights reserved.MORE
Ultraviolet A (UVA) radiation is immunosuppressive and mutagenic in humans and carcinogenic in animals. UVA suppresses immunity with a bell-shaped dose response. At doses equivalent to 15-20 minutes of sun exposure at noon, UVA contributes to approximately 75% of sunlight-induced immunosuppression. A recent action spectrum, indicating that 360-380 nm but not 320-350 nm UVA suppresses immunity in humans, suggests an important role for reactive oxygen species. UVA also causes an energy crisis in cells, and normalization of adenosine triphosphate with nicotinamide prevents UVA immunosuppression. UVA activation of the alternative complement pathway and defects in memory T-cell development are also involved. Human skin cancers contain mutations in the p53 and BRM genes that are consistent with being induced by UVA. UVA is also mutagenic in human skin equivalents. The basal layer of human skin is more susceptible to UVA-induced mutations than the upper layers. Because skin cancers arise from these basal proliferating cells, this finding is likely to be important and could be attributable to low levels of the DNA repair enzyme OGG1 in basal cells. UVA is therefore likely to make a larger contribution to UVA-induced skin carcinogenesis in humans than is predicted by small animal models as the result of being immunosuppressive and mutagenic for basal keratinocytes. Semin Cutan Med Surg 30:214-221 © 2011 Elsevier Inc. All rights reserved.MORE