Syphilis — Chancre

Contagious, systemic disease caused by Treponema pallidum

Aetiology

Causative organism:
  • Treponema pallidum subsp. pallidum
Microbiological characteristics:
  • Thin, spiral-shaped spirochete
  • Length: 6–15 μm
  • Motile (corkscrew motility)
  • Not visible on routine Gram stain
  • Fragile organism, cannot be cultured in vitro

Pathophysiology

Aquired syphilis

  • Infectious:
    • Primary syphilis: incubation period 2-3 weeks (range 9-90 days): local infection
    • Secondary syphilis: incubation period 6-12 weeks (range 1-6 months): generalised infection
    • Early latent syphilis: asymptomatic syphilis of less than two years' duration
  • Non-infectious:
    • Late latent syphilis: asymptomatic syphilis of two years' duration or longer
    • Late symptomatic syphilis (tertiary syphilis)

Congenital syphilis

  • Mother to child transmission

Clinical presentation

Primary Syphilis

Incubation period:
  • 9–90 days (average ~21 days)
Primary lesion – Chancre:
  • Single, painless ulcer
  • Clean base
  • Indurated (hard) margins
  • Non-tender
  • Heals spontaneously in 3–6 weeks
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Common sites:
  • Genitalia
  • Anus
  • Oral cavity
Regional lymphadenopathy — Bubo:
  • Bilateral
  • Firm, rubbery
  • Non-tender

Secondary Syphilis

Occurs 6–12 weeks after primary lesion.

Cutaneous and Mucocutaneous Features (Dermatology Focus)

  • Generalized maculopapular rash
    • Involves palms and soles — copper-penny rash (classic)
  • Papulosquamous lesions
  • Condylomata lata (moist, flat-topped papules in intertriginous areas)
  • Mucous patches (oral/genital)
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Systemic Features

  • Fever
  • Malaise
  • Sore throat
  • Generalized lymphadenopathy
  • Hepatosplenomegaly
Highly infectious stage

Latent Syphilis

Defined by positive serology with no clinical signs.

Classification:

  • Early latent: < 1 year
  • Late latent: > 1 year or unknown duration
Venereology importance:
  • Sexual transmission occurs mainly in early latent stage
  • Vertical transmission possible at any latent stage

Tertiary Syphilis

Occurs years to decades after initial infection.

1. Gummatous Syphilis

  • Granulomatous lesions (gummas)
  • Affect skin, bones, liver
  • Destructive but non-infectious

2. Cardiovascular Syphilis

  • Aortitis
  • Ascending aortic aneurysm
  • Aortic regurgitation

3. Neurosyphilis

Can occur at any stage
  • Asymptomatic neurosyphilis
  • Meningovascular syphilis
  • General paresis
  • Tabes dorsalis

Congenital Syphilis

Early Congenital Syphilis

  • Snuffles
  • Rash
  • Hepatosplenomegaly
  • Osteochondritis

Late Congenital Syphilis

  • Hutchinson triad:
    • Hutchinson teeth
    • Interstitial keratitis
    • Sensorineural deafness

Investigations

Direct Detection

  • Dark-field microscopy (chancre, condyloma lata)
  • PCR (limited availability)

Non-direct Detection — Serological Tests

Non-treponemal Tests (Screening & Monitoring)

  • VDRL
  • RPR
Characteristics:
  • Quantitative
  • Titers correlate with disease activity
  • False positives possible

Treponemal Tests (Confirmatory)

  • TPHA
  • FTA-ABS
  • EIA
Characteristics:
  • Highly specific
  • Usually remain positive for life

Management

Early syphilis (Primary & Secondary)

  • Benzathine penicillin 2.4 MU IM SD (first-line)
  • Doxycyclin 100mg BID PO for 30 days
  • Erythromycin 500mg QID PO for 30 days → safe in pregnancy

Late syphilis

  • Benzathine penicillin 2.4 MU IM weekly x 3 weeks

Follow-up

  • Clinical and serological evaluation → months 1, 3, 6, and 12
  • Until RPR is negative or serofast