A 6-year-old unvaccinated child from rural India presents with a thick, adherent, greyish-white pseudomembrane over the tonsils and pharynx, along with low-grade fever and cervical lymphadenopathy. Which is the most common site of diphtheria in this patient?

Explanation

## Most Common Site of Diphtheria **Key Point:** Pharyngeal (faucial) diphtheria is the most common form, accounting for approximately 90% of all diphtheria cases, followed by laryngeal, cutaneous, and nasal variants. ### Clinical Presentation of Pharyngeal Diphtheria - **Pseudomembrane characteristics:** - Thick, adherent, greyish-white or yellowish membrane - Covers tonsils, soft palate, pharyngeal wall - Bleeds if forcibly removed (unlike true membrane in strep throat) - Extends beyond the tonsils in severe cases - **Associated features:** - Low-grade fever (usually < 39°C) - Sore throat - Cervical lymphadenopathy ("bull neck" appearance in severe cases) - Foul-smelling breath - Difficulty swallowing ### Frequency of Diphtheria Sites | Site | Frequency | Key Features | |------|-----------|-------------| | Pharyngeal | ~90% | Most common; classic presentation | | Laryngeal | ~5–10% | Croup-like symptoms; airway risk | | Cutaneous | ~2–5% | Wound infection; rare in vaccinated | | Nasal | <1% | Mild; often missed; chronic carrier state | **High-Yield:** The pseudomembrane in pharyngeal diphtheria is pathognomonic and results from toxin-mediated necrosis and fibrin deposition, not bacterial invasion. **Clinical Pearl:** The "bull neck" appearance (massive cervical edema and lymphadenopathy) is a sign of severe systemic toxemia and indicates high risk of myocarditis and respiratory compromise.