A 32-year-old man from rural Maharashtra presents with a painless, indurated ulcer on the glans penis for 3 weeks, with firm, non-tender inguinal lymphadenopathy. Dark-field microscopy of the ulcer exudate shows motile spirochetes. Regarding the diagnosis and management of syphilis, all of the following are true EXCEPT:

Question

Accepted Answer

A. Tetracycline 500 mg orally four times daily for 28 days is an acceptable alternative for penicillin-allergic patients with primary syphilis. ## Clinical Management of Primary Syphilis

### Case Context
The clinical presentation (painless indurated ulcer = chancre, firm non-tender lymphadenopathy, dark-field positive spirochetes) confirms primary syphilis caused by T. pallidum.

### Correct Statements (Options 0, 1, 2)

**Key Point:** Benzathine penicillin G 2.4 million units IM single dose is the gold-standard first-line treatment for primary syphilis [cite:Harrison 21e Ch 211].

**High-Yield:** Non-treponemal tests (RPR, VDRL) are quantitative, correlate with disease activity, and typically become negative or low-titer after successful treatment. Treponemal tests (FTA-ABS, TP-PA) remain positive indefinitely.

**Clinical Pearl:** All patients with syphilis should be screened for HIV (high co-infection risk in India) and neurosyphilis (CSF examination if neurological symptoms, high RPR titer, or CD4 <50 cells/μL).

### Incorrect Statement (Option 3 — THE ANSWER)

**Warning:** Tetracycline is NOT recommended for primary syphilis in penicillin-allergic patients. Tetracyclines have poor CNS penetration and cannot reliably prevent neurosyphilis.

**High-Yield:** For penicillin-allergic patients with primary/secondary syphilis, the alternatives are:
  1. **Ceftriaxone 1 g IM daily for 10–14 days** (preferred; good CNS penetration)
  2. **Azithromycin 500 mg daily for 10–14 days** (if cephalosporin allergy; emerging resistance)
  3. **Doxycycline 100 mg twice daily for 28 days** (NOT tetracycline; doxycycline has better tissue penetration)

**Mnemonic:** **PENICILLIN ALLERGY REGIMENS (Primary/Secondary)**
- **C**eftriaxone (1 g IM daily × 10–14 days) — FIRST alternative
- **A**zithromycin (500 mg daily × 10–14 days) — if cephalosporin allergy
- **D**oxycycline (100 mg BD × 28 days) — acceptable but inferior to ceftriaxone
- **T**etracycline — NOT recommended (poor CNS penetration)

### Why Tetracycline Fails

| Parameter | Tetracycline | Doxycycline | Ceftriaxone |
| --- | --- | --- | --- |
| CNS penetration | Poor | Moderate | Excellent |
| Neurosyphilis prevention | Unreliable | Better | Reliable |
| Recommendation | NOT recommended | Acceptable | Preferred |

Answer

B. The patient should be evaluated for HIV co-infection and neurosyphilis given the clinical presentation

Answer

C. Benzathine penicillin G 2.4 million units IM in a single dose is the first-line treatment for primary syphilis

Answer

D. Serological tests include non-treponemal tests (RPR, VDRL) which become negative after successful treatment

Explanation

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