chancre

A chancre is the primary lesion of syphilis, produced by infection with Treponema pallidum. It is a painless, indurated ulcer that arises at the site of inoculation and is most common on the genitals, but can occur on the mouth, lips, hands, or other areas. The lesion typically reflects localized spirochetal infection.

Onset usually occurs about three weeks after exposure, though the range can be shorter or longer. The chancre is commonly solitary and has a clean base with firm, raised borders. It is typically painless and often accompanied by regional lymphadenopathy. Without treatment, the chancre generally heals spontaneously within three to six weeks.

Diagnosis involves clinical recognition supported by microbiology and serology. Spirochetes can be demonstrated in lesion material by dark-field microscopy or nucleic acid amplification tests. Serologic testing shows non-treponemal tests (such as RPR or VDRL) that may be negative early but become positive within weeks, and treponemal tests (such as FTA-ABS or TPPA) that usually remain positive for life. Because a chancre can resemble other ulcers, patients are often treated for syphilis while confirmatory results are pending.

Differential diagnosis includes chancroid (a painful ulcer caused by Haemophilus ducreyi), herpes simplex ulcers, aphthous ulcers, and other genital lesions. If untreated, secondary syphilis can develop weeks to months later, and later stages can occur years after exposure.

Treatment follows guidelines for early syphilis. The preferred regimen is a single intramuscular dose of benzathine penicillin G. Alternatives include doxycycline or tetracycline for those with penicillin allergy, with treatment decisions guided by pregnancy status and local guidelines. Follow-up includes periodic serologic testing to ensure an appropriate response.