A 28-year-old man presents with a painless, indurated ulcer on the glans penis with a clean base and raised borders. Regional lymph nodes are enlarged, non-tender, and mobile. Dark-field microscopy of the ulcer exudate reveals motile spirochetes. Which is the most common site of the primary chancre in males?

Explanation

## Most Common Site of Primary Chancre in Males **Key Point:** The glans penis is the most common site of primary chancre in heterosexual males, accounting for approximately 70–80% of cases. ### Anatomical Distribution of Primary Chancre | Site | Frequency in Males | Clinical Notes | |------|-------------------|----------------| | Glans penis | 70–80% | Most common; easily visible; prompts early care | | Shaft of penis | 10–15% | Less common; may be overlooked | | Perianal region | 5–10% | More common in MSM; often missed | | Oral mucosa | 2–5% | Rare; may mimic aphthous ulcer | | Other sites (fingers, breasts) | <2% | Occupational or accidental inoculation | ### Clinical Features of Primary Chancre **High-Yield:** The chancre is classically described as: 1. **Painless** — distinguishes it from herpes (painful) and haemophilus ducreyi (painful) 2. **Indurated** — firm, cartilaginous consistency 3. **Clean base** — no purulent exudate 4. **Raised borders** — sharply demarcated 5. **Solitary** — usually one lesion (though multiple chancres can occur) ### Regional Lymphadenopathy **Clinical Pearl:** Regional lymph nodes enlarge 1–2 weeks after the chancre appears. The nodes are: - Non-tender (unlike suppurative lymphadenitis) - Mobile and non-adherent - Firm and rubbery - This constellation is called **inguinal bubo** (though true buboes are suppurative) ### Diagnostic Confirmation **Key Point:** Dark-field microscopy or direct fluorescent antibody testing of exudate shows motile, corkscrew-shaped *Treponema pallidum* spirochetes — the gold standard for primary syphilis diagnosis. **Mnemonic: VDRL/RPR timing — VDRL/RPR becomes positive in primary syphilis in ~70% of cases; FTA-ABS and TP-PA are positive in >95%.** ### Why Glans is Most Common The glans penis is the most common site because: 1. It is the primary site of sexual contact in heterosexual transmission 2. The thin epithelium and microtrauma during intercourse facilitate inoculation 3. Visibility at this site often leads to earlier diagnosis and treatment [cite:Park 26e Ch 23]