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Human papillomavirus infection

Human papillomavirus (HPV) infection is widespread throughout the general population, most commonly causing cutaneous and anogenital warts by infecting epithelial cells of the skin and mucous membranes. Infection of the respiratory tract occurs less frequently. Transmission of HPV occurs via close contact with infected individuals. Minor breaks in the skin and mucous membranes are suspected to be important in the establishment of HPV infection. Because cell-mediated immunity plays a prominent role in the control of HPV infection, organ transplant recipients are particularly susceptible to HPV infection, leading to frequent and sometimes extensive warts in both adults and children (1–3). In addition to the cosmetic concerns with warts, the combined effects of HPV infection, immunosuppression and ultraviolet radiation appear to predispose transplant recipients to the development of premalignant skin keratoses and skin cancer (4,5). Actinic keratoses some of which have been associated with HPV, occur frequently in transplant recipients compared to the general population, with a mean occurrence of 38% after 5 years of immunosuppression (6). Skin cancer is the most common malignancy arising in the post-transplantation setting with a 50–100-fold increase in incidence when compared with the general population. Squamous cell carcinoma (SCC) is the most common skin cancer, which develops from warts or actinic lesions and occurs 20 years earlier, on average, than in individuals who are not immunosuppressed. Although basal cell carcinoma occurs more frequently in the immunocompetent population, transplant recipients more frequently develop squamous cell carcinomas (SCCs) (7). Skin cancers in transplant recipients are often characterized by a rapid course and by more frequent node metastases than in the general population and these may be life-threatening (8).