Recallab › Question bank › Dermatology › #50359
Painless genital ulcer
A 26-year-old woman has a single genital ulcer that appeared three weeks ago. It is painless, has a clean base and a firm indurated edge, and there is rubbery, non-tender bilateral inguinal lymphadenopathy. What is the most likely diagnosis?
- A. Chancroid
- correctB. Primary syphilis
- C. Genital herpes
- D. Lymphogranuloma venereum
Explanation
Key fact
Painless plus indurated plus clean base equals a syphilitic chancre. Pain is the single most useful discriminator among genital ulcers.
Primary syphilis. The nodes are enlarged, rubbery and painless, which matches the ulcer.
Why
The chancre appears about three weeks after exposure.
It is classically single, painless and indurated, with a clean base.
The lymphadenopathy is bilateral, rubbery and non-tender.
It heals without treatment, which is why patients present late or not at all.
Dark-ground microscopy or a treponemal serological test confirms it.
Genital ulcers compared
Why not the others
- A. Chancroid — gives multiple painful ulcers with ragged undermined edges and a purulent base, with tender nodes that may suppurate.
- C. Genital herpes — produces crops of small painful vesicles that erode, usually with tender nodes and prodromal burning.
- D. Lymphogranuloma venereum — has a small transient painless ulcer, but the presentation is the bubo - large, tender and fluctuant, often with a groove sign.
Remember
Painless and hard is syphilis; painful and soft is chancroid.
Go deeper
A single intramuscular dose of benzathine penicillin treats primary, secondary and early latent disease; late latent disease needs three weekly doses.
The Jarisch-Herxheimer reaction - fever and myalgia hours after the first dose - is expected, not an allergy, and matters especially in pregnancy.
Any genital ulcer is an opportunity to test for HIV, since ulcerative disease markedly increases transmission in both directions.
Fitzpatrick's Dermatology, 9th ed. (McGraw Hill, 2019); Harrison's Principles of Internal Medicine, 22nd ed. (McGraw Hill, 2025).