Paper I
Question
Patient presents with a painless indurated ulcer on the external genitalia for three months, probable causative agent
Answer
- [x] a) Treponema pallidum
A painless, indurated ulcer (chancre) on the genitalia, persisting for weeks (as in this three-month history), is the classical presentation of primary syphilis, caused by Treponema pallidum. This is distinguished from other genital ulcer diseases by its painlessness and induration — herpes simplex virus classically causes painful, grouped vesicular/ulcerative lesions; Haemophilus ducreyi (chancroid) causes a painful, ragged, non-indurated (“soft”) ulcer with tender lymphadenopathy; and molluscum contagiosum causes small, painless, umbilicated papules, not an ulcer.