Syphilis (Treponema pallidum infection)
Syphilis is a sexually transmitted infection with the spirochete Treponema pallidum that progresses through painless chancre (primary), disseminated rash and condyloma lata (secondary), latent, and tertiary stages including neurosyphilis, diagnosed by paired nontreponemal and treponemal serology and treated with a single dose of intramuscular benzathine penicillin G for early disease.
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What this article covers
- Overview
A sexually transmitted spirochetal infection that progresses through distinct, predictable clinical stages if untreated: Treponema pallidum causes primary disease (painless chancre), secondary…
- Epidemiology
Incidence of primary and secondary syphilis has been rising in the United States since 2000: this, alongside rising gonorrhea and chlamydia rates, reflects an ongoing resurgence of bacterial sexually transmitted infection (STI) rates.
- Risk factors
Unprotected sexual contact with an infected partner, especially with multiple or anonymous partners: condomless intercourse, a new partner in the preceding 60 days, or a partner recently treated for an STI are the principal behavioral risks.
- Pathophysiology
Treponema pallidum enters through microabrasions in skin or mucosa during sexual contact: the spirochete penetrates intact or minimally abraded mucosal surfaces at the contact site, establishing local infection.
- Clinical features
Primary syphilis: a single painless genital chancre with a raised, indurated, regular border, appearing 1 week to 3 months after exposure: often unrecognized because it is painless and heals…
- Differential diagnosis
Herpes simplex virus genital infection (primary-stage mimic, most common cause of genital ulcer): multiple, painful vesicles or shallow ulcers rather than a single painless indurated chancre…
- Diagnosis
The diagnosis is confirmed by paired nontreponemal (RPR or VDRL) and treponemal (FTA-ABS or TPPA) serology, since neither alone is both sensitive and specific; there is no numeric severity grade, and…
- Management
First, stage the infection (primary, secondary, early latent, late latent/unknown duration, or neurosyphilis), since staging sets the regimen and duration; treat empirically before serology returns…
- Complications
Neurosyphilis at any stage, including meningovascular stroke, tabes dorsalis, and general paresis: untreated disease produces irreversible deficits.
- Prognosis
Early-stage disease has an excellent prognosis with a single dose of benzathine penicillin: curative in the great majority of patients, with the expected fourfold decline in titers by 12 months confirming response.
- Prevention
Universal syphilis serologic screening in all pregnant women, at entry to prenatal care: the USPSTF recommends screening every pregnant woman given the rising risk of congenital transmission.
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