Although receptive anal intercourse (RAI) is far from the sole preserve of men who have sex with men (MSM), the medical consequences of this sexual behaviour and resulting infection with human papillomavirus (HPV) are becoming increasingly apparent in this population. It is over 25 years since Daling et al reported on the increased rates of anal cancer in never married men with positive syphilis serology—their proxy for MSM.1 These rates of up to 35:100 000 were similar to those of cervical cancer before the institution of routine cervical cytology screening, and much greater than the rate of 2:100 000 seen currently in the general population. Since then, MSM have borne the brunt of the HIV epidemic in Western society and, paradoxically, with the now widespread availability and impact of highly active antiretroviral therapy, we are now seeing rates of anal cancer in HIV positive MSM that are more than double those initially reported.2 In contrast to other AIDS-associated malignancies, such as Kaposi’s sarcoma, anal cancer rates continue to increase, a fact that clinicians, MSM and the HIV community at large seem, for the most part, unable or unwilling to address.

THE ANAL CANAL

The anal canal is 3–4 cm long and is lined with stratified squamous non-keratinising epithelium. It extends from the anal verge to the anorectal transition zone where it meets the unicellular columnar epithelium of the rectum. For the most part, it is only the anal canal and not the rectum that becomes infected with HPV.

HPV

In the general population, anogenital HPV is the most common viral sexually transmitted infection. Supporting data from serological studies indicate that over 50% of sexually active North Americans have antibodies indicative of previous exposure to anogenital HPV.3 HPV is both highly infectious and easily transmitted as demonstrated in a recent study showing …