What are the characteristics of a syphilis rash and how is it treated?

Characteristics of Syphilis Rash and Treatment

Syphilis rash typically presents as a non-itchy, non-painful maculopapular eruption that prominently involves the palms and soles, and is treated with benzathine penicillin G as the first-line therapy for all stages of infection. 1, 2

Clinical Presentation of Syphilis Rash

Primary Stage

• Characterized by a solitary, painless chancre at the site of inoculation 2
• Usually appears 3-4 weeks after infection
• Heals spontaneously within 3-6 weeks even without treatment

Secondary Stage (Classic Rash)

• Appears 2-8 weeks after the primary chancre
• Key characteristics:
  • Diffuse, symmetrical maculopapular rash
  • Classically involves palms and soles (highly distinctive feature) 3
  • Typically non-itchy and non-painful
  • Copper-red or ham-colored lesions
  • May affect the entire body including mucous membranes 4
• Associated findings:
  • Condyloma lata: raised, fleshy, highly infectious lesions in moist areas 4
  • Generalized lymphadenopathy
  • Systemic symptoms: fever, malaise, headache, sore throat 5

Latent and Tertiary Stages

• Latent stage: no visible skin manifestations, diagnosed only by serology 2
• Tertiary stage: may present with gummatous lesions (nodular, ulcerative lesions of the skin and bones) 5

Diagnosis

• Dark-field microscopy of lesion exudate (if available)
• Serologic testing:
  • Screening with non-treponemal tests (RPR or VDRL)
  • Confirmation with treponemal-specific tests 2

Treatment Guidelines

First-line Treatment

• Primary, Secondary, and Early Latent Syphilis (< 1 year duration):

  • Benzathine penicillin G 2.4 million units IM in a single dose 1, 6

• Late Latent Syphilis or Latent Syphilis of Unknown Duration:

  • Benzathine penicillin G 7.2 million units total, administered as 3 doses of 2.4 million units IM at 1-week intervals 1

• Neurosyphilis:

  • Penicillin G aqueous 18-24 million units IV daily, administered as 3-4 million units every 4 hours for 10-14 days 1

Alternative Regimens (for non-pregnant, penicillin-allergic patients without neurosyphilis)

• Doxycycline 100 mg orally twice daily for 14 days (early) or 28 days (late)
• Tetracycline 500 mg orally four times daily for 14 days (early) or 28 days (late) 1

Special Populations

• Pregnant women: Penicillin is the only proven effective treatment; desensitization required if allergic 1
• HIV-infected patients: Same regimens as HIV-negative patients but require closer follow-up 1

Treatment Monitoring

• Quantitative non-treponemal test titers (RPR or VDRL) should be obtained at baseline
• Follow-up titers at 6,12, and 24 months after treatment
• Successful treatment should show a fourfold decline in titers within:
  • 6 months for primary/secondary syphilis
  • 12-24 months for latent/late syphilis 1, 2

Important Considerations

• Jarisch-Herxheimer reaction: acute febrile reaction with headache and myalgia within 24 hours of treatment, especially common in early syphilis 6
• Partner notification and treatment is essential:
  • Sexual contacts within 90 days of diagnosis should be treated presumptively even if seronegative
  • Contacts from >90 days should be treated presumptively if follow-up is uncertain 6, 1
• Treatment failure should be suspected if:
  • Signs or symptoms persist or recur
  • Four-fold increase in non-treponemal test titers
  • Failure of titers to decrease four-fold within expected timeframe 1

Common Pitfalls

• Misdiagnosis due to varied presentations - always consider syphilis in any unusual rash, especially involving palms and soles
• Inadequate follow-up after treatment
• Failure to identify and treat sexual contacts
• Using macrolides empirically (resistance has emerged) 5
• Overlooking neurosyphilis, which can occur at any stage and requires CSF examination for diagnosis 2