A review of photodynamic therapy for the treatment of viral skin diseases.

Introduction: Photodynamic therapy (PDT) is a two-stage treatment method making use of light energy and a photosensitizer in the presence of oxygen. PDT has already proved to bring good anti-inflammatory and anti-proliferative effects in the treatment of actinic keratosis, squamous cell carcinoma in situ as well as in superficial and nodular basal cell carcinoma. In PDT-treated lesions, infected or cancerous keratinocytes are effectively destroyed due to selective apoptosis and necrosis induced by a release of reactive oxygen species. PDT is distinguished by several features, most notably its non-invasiveness, selectivity for the target tissue, which causes fewer side effects and brings excellent cosmetic results. PDT is an effective option for treating viral diseases using a photosensitizer capable of selective accumulation in virus-infected cells not only within visible lesions, but also in subclinical disease areas where the virus is in latent form. Objectives and methods: This literature review presents recent reports on PDT for the treatment of viral skin infections, with a particular focus on the efficacy of this method. Results: The viruses that most commonly cause skin diseases include the human papilloma virus (HPV), herpes simplex virus (HSV), varicella-zoster virus (VZV), molluscum contagiosum virus (MCV). PDT inhibits the proliferation of virus-infected cells, induces apoptosis, damages lesional blood vessels, regulates local immunity and controls viral loads. An additional advantage of PDT is the short healing period and little damage to the treated tissue. Furthermore, wider use of PDT may contribute to reducing the risk of developing drug resistance. Conclusion: The safety of PDT makes this method an effective way to treat viral skin diseases in difficult locations, as well as in children and immunocompromised patients.