Secondary Syphilis Rash
Secondary syphilis characteristically presents with macular, maculopapular, papulosquamous, or pustular skin lesions that typically begin on the trunk and spread peripherally to involve the palms and soles—this palm and sole involvement is the pathognomonic feature that distinguishes it from most other rashes. 1
Classic Rash Characteristics
- Morphology: The rash progresses from small (1-5 mm), blanching, pink macules to maculopapular lesions, sometimes with central petechiae 1
- Distribution pattern: Begins on trunk → spreads to extremities → characteristically involves palms and soles → usually spares the face 1
- Color: Described as erythematous to copper-colored macules and papules 2
- Symptoms: Typically nonpruritic (not itchy) 2
- Timing: Appears 2-4 days after fever onset, occurring 2-8 weeks after primary inoculation 1
Additional Cutaneous Manifestations
- Condyloma lata: Moist, flat, papular lesions in warm intertriginous regions (groin, axillae, perianal areas) that can resemble papillomavirus infection 1
- Mucous membrane lesions: Can involve oral and genital mucosa 3
- Generalized lymphadenopathy: Accompanies the rash in most cases 1
Systemic Symptoms Accompanying the Rash
- Fever, malaise, anorexia 1
- Arthralgias and headache 1
- Sore throat and night sweats 2
- Constitutional symptoms persist from days to several weeks before resolving 1
Important Clinical Pitfalls
Absence of rash does not exclude secondary syphilis—less than 50% of patients have a rash in the first 3 days of illness, and a smaller percentage never develop a rash 1. The rash may be atypical, localized, faint, or evanescent 1.
Skin pigmentation can obscure the rash, making recognition more difficult in patients with darker skin tones 1.
HIV co-infection alters presentation: HIV-infected patients may have more apparent clinical lesions, accelerated disease progression, and atypical presentations including rapidly progressive papulopustular lesions 1, 3.
Atypical Presentations to Consider
- Purpuric eruption: Can mimic leukocytoclastic vasculitis with rapidly progressive purpuric papules 2
- Hyperpigmented macules: May be mistaken for Kaposi sarcoma in HIV patients 3
- Diffuse maculopapular rash: Can be confused with drug reactions or DRESS syndrome 4
Diagnostic Confirmation
The diagnosis requires both clinical recognition and serologic confirmation with nontreponemal tests (VDRL or RPR) and treponemal tests (FTA-ABS or MHA-TP) 1. Skin biopsy with immunohistochemical staining can confirm the presence of Treponema spirochetes when the diagnosis is uncertain 4, 2, 3.