Syphilis

Lues, lues venerea, hard chancre, French disease, Schaudinn’s disease.

Syphilis is a sexually transmitted infectious disease caused by the bacterium Treponema pallidum subspecies pallidum. Transmission occurs primarily through sexual contact (acquired syphilis), and more rarely congenitally via transplacental transmission (congenital syphilis).

In many industrialized countries, especially among men who have sex with men (MSM), the incidence of syphilis has increased again in recent years. In Switzerland, syphilis cases nearly doubled over the past decade: from 616 reported cases in 2013 to 1,056 in 2022. Coinfection with HIV is common.

Syphilis is clinically classified into:

• Early syphilis (Stage I & II, ≤1 year after infection)
• Late syphilis (Stage III, >1 year after infection)
• Neurosyphilis (can occur at any stage)
• Congenital syphilis (early/late)

Transmission occurs through direct contact with infectious lesions, especially during sexual contact. Hematogenous and lymphatic dissemination allows systemic spread. The humoral immune response plays a central role but is not protective.

Stage I: After 2–3 weeks: painless ulcer (ulcus durum) at the site of infection, regional lymphadenopathy
Stage II: After 6–12 weeks: generalized lymphadenopathy, maculopapular exanthema (including palms and soles), mucous membrane plaques, syphilitic alopecia, systemic symptoms
Stage III: Years later: gummas, cardiovascular syphilis, neurosyphilis with tabes dorsalis and progressive paralysis
Neurosyphilis: Headaches, psychiatric symptoms, gait disturbances, CSF pleocytosis

Diagnosis is guided by clinical presentation and medical history. Confirmation is based on serologic tests:

• Screening: TPHA, CLIA, EIA
• Confirmation: FTA-Abs
• Disease activity: VDRL/RPR

In suspected neurosyphilis: CSF analysis (cell count, protein, CSF-VDRL), possibly PCR. In early stages: dark-field microscopy or PCR from lesions.

Primary lesions typically appear on the genitals, rectum, or oral cavity. Secondary skin manifestations are generalized, often including palms and soles. Gummas preferentially affect skin, bones, and internal organs.

Unprotected sexual contact, MSM, anonymous partners, HIV coinfection. In up to 60% of cases, the primary stage goes unnoticed.

Early stages show lymphoplasmacytic infiltrates and vasculitic changes. Gummas present as granulomatous inflammation with central necrosis.

Neurosyphilis, cardiovascular syphilis (e.g., aortic aneurysm), ocular involvement, congenital syphilis with early/late damage. Increased risk of HIV transmission due to ulcerations.

Good prognosis with early diagnosis and treatment. If untreated, the disease progresses chronically with potentially severe organ involvement.

Safer sex practices, regular screening in at-risk populations (e.g., MSM, HIV-positive individuals). Testing during the first trimester of pregnancy, with repeat testing if needed. Partner treatment is essential.

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