A 28-year-old man from Delhi presents to the STI clinic with a painless ulcer on the glans penis for 3 weeks. On examination, the ulcer has a punched-out appearance with a clean base and indurated edges. Regional lymph nodes are enlarged, non-tender, and rubbery. Serum RPR is positive at 1:16 dilution. Dark-field microscopy of ulcer exudate shows motile spirochetes. What is the most likely clinical stage of syphilis?

## Clinical Diagnosis: Primary Syphilis ### Key Features Present **Key Point:** Primary syphilis is defined by the presence of a chancre — a single, painless, indurated ulcer with a clean base and sharply demarcated borders. This patient presents with the classic hallmark of primary syphilis: - **Painless ulcer** (distinguishes from herpes, which is painful) - **Punched-out appearance** with clean base - **Indurated (hard) edges** — the hallmark of a chancre - **Duration < 6 weeks** (typical window: 3–90 days post-exposure) - **Regional lymphadenopathy** (non-tender, rubbery nodes — "bulletproof" nodes) - **Positive dark-field microscopy** — confirms *Treponema pallidum* ### Serological Correlation **High-Yield:** In primary syphilis, RPR/VDRL becomes positive only in the **final 1–2 weeks** of the chancre's appearance. This patient's positive RPR at 1:16 is consistent with early primary syphilis. ### Differential Staging | Stage | Ulcer | Systemic Signs | Serology | Duration | |-------|-------|---|---|---| | **Primary** | Single chancre, painless, indurated | Lymphadenopathy only | RPR/VDRL +, FTA-ABS + | 3–90 days | | **Secondary** | Rash (maculopapular, palms/soles), mucous patches, condylomata lata | Fever, malaise, hepatosplenomegaly, meningitis | RPR/VDRL ++ (high titer) | 4–10 weeks post-chancre | | **Tertiary** | Gummas (destructive lesions) | Neurosyphilis, cardiovascular involvement | RPR/VDRL variable, FTA-ABS + | Years to decades | | **Latent** | No lesions | Asymptomatic | Serology + | Variable | ### Clinical Pearl **Clinical Pearl:** The **chancre is self-limited** — it heals spontaneously in 3–6 weeks even without treatment. The progression to secondary syphilis (rash, systemic symptoms) occurs 4–10 weeks after the chancre appears, often while the ulcer is still healing or has already resolved. ### Why Dark-Field Microscopy Matters **Key Point:** Dark-field microscopy demonstrating motile spirochetes is **pathognomonic for primary syphilis** and confirms *Treponema pallidum* before serology becomes fully positive.