ABSTRACT
Sexual activity has been the most important risk factor for genital human papillomavirus (HPV) infection in many previous studies (1). Likewise, sexual transmission has been the major form of acquisition of human immunodeficiency virus (HIV) infection. Because of shared risk factors, it is not surprising that anogenital HPV infection is common among HIV-positive men and women. In HIV-positive women, much attention has been devoted to cervical HPV infection and HPVassociated lesions, including cervical cancer and its precursor, cervical squamous intraepithelial lesion (CSIL). In HIV-positive men, most attention has focused on anal HPV infection and anal SIL (ASIL). Compared with cervical HPV infection and CSIL, our understanding of the natural history of anal HPV infection and ASIL is very limited. Only recently have methods developed for investigation of CSIL been applied to ASIL. However, recent data summarized in this chapter point to a high incidence and prevalence of ASIL in HIV-positive homosexual and bisexual (hereafter called homosexual) men. Although there are no direct data demonstrating that ASIL progresses to invasive anal cancer, the strong similarities with CSIL and the high incidence of anal cancer in populations known to have high rates of ASIL suggest that ASIL is likely to be the lesion from which anal cancer arises.
