Chancroid (Haemophilus ducreyi) – Painful genital ulcer with gray to yellow exudate, inguinal adenopathy (often unilateral); can rupture and drain pus. Organisms clump in parallel strands ("school of fish").

Chlamydia (Chlamydia trachomatis D-K) – Urethritis, cervicitis, epididymitis, conjunctivitis, reactive arthritis, PID

Condylomata acuminata (HPV-6, -11) – Genital warts, koilocytes

Genital herpes (HSV-2) – Painful penile, vulvar, or cervical vesicles and ulcers; can cause systemic symptoms such as fever, headache, myalgia. Multinucleated giant cells and Cowdry A inclusions.

Gonorrhea (Neisseria gonorrhoeae) – Urethritis, cervicitis, PID, prostatitis, epididymitis, arthritis, creamy purulent discharge

Granuloma inguinale, donovanosis (Klebsiella granulomatis) – Painless, beefy red ulcer that bleeds readily on contact. No lymphadenopathy. Uncommon in US. Cytoplasmic Donovan bodies (bipolar staining) on microscopy.

Lymphogranuloma venereum (Chlamydia trachomatis L1-3) – Infection of lymphatics; painless shallow genital ulcers; large, painful, coalesced lymphadenopathie (ie, buboes)

Syphilis (Treponema pallidum) – 1° painless chancre (single, indurated, well-circumscribed ulcer), 2° condylomata lata, 3° gummas