Pathology · single question
A sexually active 23-year-old has an irritated lesion on the lower lip mucosa. Most likely causative organism?
Show answer and explanation
Correct answer: D. Treponema pallidum
Treponema pallidum causes syphilis. A painless, indurated ulcer (chancre) on the lip in a sexually active young adult is the primary syphilitic lesion.
- A. ❌ HSV causes painful vesicular lesions, not a solitary indurated ulcer.
- B. ❌ Candida causes white plaques or erythematous patches, not an indurated ulcer.
- C. ❌ HPV causes papillary/warty lesions, not an indurated ulcer.
- D. ✅ CORRECT – T. pallidum: primary chancre is painless and indurated; lip is a known extragenital site.