[A male with perianal skin abnormalities].

A 23-year-old man who has sex with men with perianal pain and blood loss showed erosive perianal plaques. PCR swab of the plaque was positive for Treponema pallidum and herpes simplex virus (HSV) type 2. Patient was diagnosed with primary or secondary syphilis with a co-infection of HSV and was successfully treated with benzathine benzylpenicillin.