Secondary Syphilis: Clinical Features, Diagnosis, and Treatment

Secondary syphilis occurs 4-10 weeks after primary chancre, representing hematogenous dissemination of Treponema pallidum. It is the "great imitator" with diverse manifestations.

Clinical Features

• Rash: Maculopapular, copper-colored, non-pruritic, involving trunk, extremities, palms and soles (pathognomonic). May be annular, pustular, or condyloma lata (moist, infectious papules in intertriginous areas).
• Mucous patches: Snail-track ulcers on oral/genital mucosa — highly infectious.
• Constitutional: Fever, malaise, headache, pharyngitis, generalized lymphadenopathy.
• Rare: Hepatitis, glomerulonephritis, uveitis, periostitis, meningitis.

Diagnosis

• Dark-field microscopy / PCR: Direct detection from lesion exudate (gold standard for primary/secondary).
• Serology (required):
  • Nontreponemal: RPR/VDRL — quantitative, correlates with disease activity.
  • Treponemal: FTA-ABS, TP-PA, EIA/CIA — confirmatory, usually lifelong positive.
• Typical pattern: RPR high titer (≥1:16) + positive treponemal test.

Treatment (CDC 2021 Guidelines)

• Preferred: Benzathine penicillin G 2.4 million units IM single dose.
• Penicillin allergy: Doxycycline 100 mg BID × 14 days or ceftriaxone 1 g IM/IV daily × 10-14 days. Desensitization preferred in pregnancy.
• HIV coinfection: Same regimen; closer serologic follow-up.

Follow-Up

• Clinical and RPR at 6, 12 months (24 if HIV+).
• Fourfold RPR decline indicates adequate response.
• Treat sexual partners (epidemiologic treatment if exposure within 90 days).

Key Points

• Rash resolves spontaneously but infection progresses to latent/tertiary stages without treatment.
• Neurosyphilis can occur at any stage; consider LP if neurologic signs or treatment failure.
• Congenital syphilis prevention: Screen all pregnant women at first visit, 28 weeks, delivery (high prevalence areas).