A 6-year-old unvaccinated child from rural India presents with a pseudomembrane over the tonsils and pharynx, fever, and neck swelling. A 9-year-old sibling presents with similar features but also has marked respiratory stridor and cyanosis. Which clinical feature best distinguishes laryngeal diphtheria from pharyngeal diphtheria?

Explanation

## Distinguishing Laryngeal from Pharyngeal Diphtheria ### Clinical Presentation Comparison | Feature | Pharyngeal Diphtheria | Laryngeal Diphtheria | |---------|----------------------|---------------------| | **Pseudomembrane location** | Tonsils, soft palate, uvula | Vocal cords, subglottic region | | **Stridor** | Absent | Present (inspiratory or biphasic) | | **Respiratory distress** | Minimal | Severe; may progress to complete airway obstruction | | **Cyanosis** | Absent | Often present | | **Airway intervention** | Rarely needed | Frequently required (intubation/tracheostomy) | | **Mortality** | Lower | Higher due to asphyxia | ### Key Point: **Stridor and respiratory compromise are the hallmark discriminators of laryngeal diphtheria.** Pharyngeal diphtheria presents with a visible pseudomembrane but does not typically cause airway obstruction unless it extends into the larynx. ### Clinical Pearl: Laryngeal diphtheria is a medical emergency. The pseudomembrane may not be visible on oral inspection because it lies below the vocal cords. Diagnosis relies on clinical suspicion (stridor + fever + unvaccinated status) and direct laryngoscopy. ### High-Yield: **Laryngeal diphtheria = "croupy" presentation with stridor and risk of asphyxia.** This distinguishes it from the more common pharyngeal form, which is usually self-limited without airway compromise. ### Warning: Do not confuse laryngeal diphtheria with viral croup (parainfluenza). Diphtheria laryngitis has a more gradual onset, systemic toxicity, and a tougher pseudomembrane; croup is typically more acute and viral prodrome-associated.