A painless vulvar ulcer in a sexually active woman is most suggestive of which diagnosis?

A painless vulvar ulcer in a sexually active woman is most suggestive of syphilis, specifically a primary chancre associated with primary syphilis. The characteristic chancre appears at the site of infection, is typically painless, and is often a solitary lesion. This aligns with the clinical presentation described in the question.

In primary syphilis, the ulcer may not exhibit any surrounding inflammation, and it often resolves on its own even without treatment. This is a key distinguishing feature that helps healthcare providers consider syphilis as a potential diagnosis when encountering a painless ulcer in this context.

While other conditions, like herpes, chancroid, and granuloma inguinale, can present with genital ulcers, they typically do not present the same way. Herpes often presents with painful vesicular lesions, and chancroid presents with painful ulcerative lesions accompanied by lymphadenopathy. Granuloma inguinale usually manifests with a progressive and painless ulcer but is often associated with more extensive tissue inflammation and may not be solitary.

Thus, the description of a painless vulvar ulcer distinctly points toward syphilis as the most likely diagnosis.