Laryngotracheobronchitis
Summary
Laryngotracheobronchitis ('croup') is an acute viral infection of the upper airway in children 6 months to 3 years, most often caused by parainfluenza virus type 1. Classic features: barking 'seal-like' cough, inspiratory stridor, hoarseness, and the 'steeple sign' on neck X-ray.
Detail
Parainfluenza virus type 1 (a paramyxovirus) is the most common cause; type 3 also frequent. Infection causes subglottic edema, narrowing the already small pediatric airway and producing inspiratory stridor. Symptoms classically worsen at night. AP neck X-ray shows subglottic narrowing ('steeple sign'); contrast with epiglottitis ('thumb sign,' caused by H. influenzae type b in unvaccinated children). Treatment: humidified air, single-dose dexamethasone for all severities, and nebulized racemic epinephrine for moderate to severe stridor at rest; intubation is rare. Distinguish from bacterial tracheitis (Staph aureus, high fever, toxic appearance), foreign body aspiration (sudden onset), and epiglottitis (drooling, tripod position, no cough).
Sources
- First Aid for USMLE Step 1 2024
- Nelson Essentials of Pediatrics
- Sketchy Medical
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