Anal intraepithelial neoplasia in HIV infection.

Human papillomavirus (HPV) infections belong to the most common sexually transmitted infections worldwide. While the immune system eliminates most HPV infections over time in immunocompetent individuals, HPV infections tend to persist in immunodeficient individuals. In HIV-infected men who have sex with men (MSM), anal HPV prevalence is more than 90% and infections with multiple HPV types are common. Consequently, HPV-associated anogenital malignancies occur with high frequency in patients with HIV infection. Anal intraepithelial neoplasia (AIN) is a potential precursor lesion of squamous cell carcinoma of the anus. Like its cervical counterpart, cervical intraepithelial neoplasia (CIN), AIN is causally linked to persistent infections with high-risk HPV types such as HPV16 or HPV18. As AIN and CIN share distinct biological similar-ities, AIN screenings analogous to Pap smear programs for CIN have been recommended in high-risk populations to reduce the incidence of anal carcinoma. These screenings include cytological analysis followed by high resolution anoscopy in case of anal dysplasia. Treatment guidelines for AIN are not yet available. Therapeutic strategies can be divided into topical (e.g. trichloroacetic acid, podophyllotoxin, imiquimod, photodynamic therapy) and ablative (e. g. surgical excision, laser ablation, infrared coagulation, electrocautery) measures. However, controlled studies on AIN treatment have not been performed. The impact of HPV vaccination on AIN development will also need to be assessed. Long-term follow-up of these patients is essential to gain more insight into the natural history of anogenital HPV infection in HIV-positive MSM.