How to diagnose tertiary syphilis?

Diagnosis of Tertiary Syphilis

The diagnosis of tertiary syphilis requires a combination of clinical evaluation for characteristic manifestations (cardiovascular, neurological, or gummatous lesions), positive serological tests, and specialized testing such as CSF examination when neurosyphilis is suspected. 1, 2

Clinical Manifestations of Tertiary Syphilis

Tertiary syphilis typically presents with one or more of these major manifestations:

• Gummatous syphilis: Granulomatous lesions that can affect any organ system
• Cardiovascular syphilis: Aortitis, aortic aneurysm, aortic regurgitation, coronary artery involvement 3
• Neurosyphilis: Can occur at any stage but in tertiary syphilis presents as tabes dorsalis, general paresis, or meningovascular disease 1

Diagnostic Algorithm

Step 1: Serological Testing

• Initial screening: Perform nontreponemal test (VDRL or RPR) 1, 2
• Confirmatory testing: All reactive nontreponemal tests must be confirmed with a treponemal-specific test (FTA-ABS, TP-PA) 2, 4
• Interpretation:
  • Positive results on both tests strongly suggest current or past infection
  • In tertiary syphilis, nontreponemal titers may be low or even nonreactive in 25-30% of cases 1
  • Treponemal tests typically remain positive for life regardless of treatment 2

Step 2: Clinical Evaluation for Organ Involvement

• Cardiovascular assessment: Evaluate for aortic regurgitation, aneurysm, or coronary artery disease 3
• Neurological examination: Look for signs of meningitis, stroke, cranial nerve abnormalities, sensory ataxia, or cognitive decline 1
• Skin and mucosal examination: Check for gummatous lesions (nodular, noduloulcerative, or infiltrative lesions) 2

Step 3: CSF Examination (Critical for Neurosyphilis)

• Indications for CSF examination:

  • All patients with neurological or ocular symptoms/signs
  • Active tertiary syphilis
  • Treatment failure
  • HIV-infected persons with late latent syphilis 1, 5

• CSF findings suggestive of neurosyphilis:

  • Reactive CSF-VDRL (specific but not sensitive)
  • CSF WBC >10 cells/μL (typically mononuclear pleocytosis)
  • Elevated protein concentration
  • Note: A nonreactive CSF treponemal test (e.g., CSF FTA-ABS) can exclude neurosyphilis 1, 5

Special Considerations

HIV Co-infection

• HIV infection may alter serological responses but doesn't significantly change the performance of standard tests 5
• More frequent false-positive nontreponemal tests may occur in HIV-infected persons 1
• CSF examination is recommended for all HIV-infected persons with syphilis of unknown duration or late latent syphilis 1
• Some specialists recommend CSF examination for all HIV-infected persons with syphilis if serum RPR is ≥1:32 or CD4+ count is <350 cells/μL 1

Diagnostic Pitfalls to Avoid

• Relying on a single serologic test: Both nontreponemal and treponemal tests are required 2, 4
• Missing neurosyphilis: CSF examination is essential when neurological symptoms are present 1
• Misinterpreting persistent low-titer seropositivity: Some patients remain "serofast" after treatment 6
• Switching between different nontreponemal tests: Use the same test consistently for follow-up 6

Additional Testing When Diagnosis is Uncertain

• Biopsy of lesions with silver staining for spirochetes
• Direct fluorescent antibody testing of lesion material
• PCR-based methods (though not currently recommended for neurosyphilis) 1, 5

Follow-up After Diagnosis

• Monitor treatment response with quantitative nontreponemal tests at 3,6,12,18, and 24 months 6
• For neurosyphilis, repeat CSF examination at 3 and 6 months after therapy completion, then every 6 months until CSF normalizes 6

By systematically following this diagnostic approach, clinicians can accurately identify tertiary syphilis and initiate appropriate treatment to prevent further morbidity and mortality from this advanced stage of infection.