Anogenital warts are due to an infection of anogenital skin and mucous membranes by certain human papilloma viruses, most commonly HPV subtypes 6, 11, 16 and 18. They manifest typically as flat plaques or papillomatous, keratinous growths on and adjacent to the external genitalia and anus. Some HPV subtypes, including types 16 and 18, are oncogenic and predispose to the development of anogenital cancers.