A couple, who did not know each other very well, dated and had sexual contact. Several weeks later, the man noticed a small, painless vesicle on his penis, which ruptured and then healed. Soon, his inguinal lymph nodes enlarged and discharged pus through multiple sinus tracts. Lymphogranuloma venereum (LGV) is a venereal disease caused by serotype L1, L2, or L3 of Chlamydia trachomatis. The differential diagnosis should include which of the following?