Persistent rectal ulcer associated with human papillomavirus type 33 in a patient with AIDS: successful treatment with isotretinoin. Rectal dysplasia and carcinoma associated with human papillomavirus infection are increasing in prevalence among homosexual men, particularly those infected with the human immunodeficiency virus. We report a case involving a 39-year-old homosexual man with AIDS who developed a persistent rectal ulcer. A biopsy of the ulcer revealed severe squamous dysplasia, and human papillomavirus type 33 was detected in rectal tissue with use of in situ DNA hybridization. This genotype of virus has not been previously associated with anal or rectal dysplasia in homosexual men, including those infected with the human immunodeficiency virus. The rectal ulcer resolved after 2 months of oral therapy with 60 mg/d of isotretinoin, a retinoid. 