What is Croup?
Croup is a common childhood disease characterized by sudden onset of a distinctive barking cough, inspiratory stridor, hoarse voice, and respiratory distress resulting from upper airway inflammation and edema of the larynx, trachea, and bronchi. 1, 2
Epidemiology and Typical Presentation
- Croup is the most common cause of acute upper airway obstruction in young children, with a median age of presentation at 23 months and 63% being male patients 1, 3
- The condition typically affects children between 6 months and 6 years of age 4, 5
- Onset is usually sudden, often preceded by an upper respiratory infection, and commonly occurs in late fall or early winter 4
Clinical Features
The hallmark clinical presentation includes:
- Barking or brassy cough - the distinctive "seal-like" quality that is often recognizable even before seeing the child 6, 2
- Inspiratory stridor - particularly at rest in moderate to severe cases 1, 7
- Hoarse voice - due to laryngeal inflammation 2, 3
- Respiratory distress - with use of accessory muscles in more severe cases 1
- Low-grade fever - typically without high fever (fever >39°C suggests alternative diagnosis) 8, 4
Etiology
- Croup is most commonly caused by parainfluenza viruses (types 1-3), but can also be caused by RSV, rhinoviruses, coronaviruses, adenoviruses, influenza, and human metapneumovirus 8
- The viral infection causes inflammation and edema of the subglottic region, leading to airway narrowing 3
Types of Croup
- Viral croup - preceded by viral prodrome with upper respiratory symptoms 3
- Spasmodic croup - sudden onset without viral prodrome 3
- Recurrent croup - defined as two or more episodes per year, which should prompt evaluation for underlying structural or inflammatory airway abnormalities 3
Key Distinguishing Features from Other Conditions
Croup differs from other causes of upper airway obstruction:
- Unlike bacterial tracheitis, croup typically does not present with toxic appearance, high fever, or purulent secretions 8
- Unlike foreign body aspiration, croup usually has antecedent upper respiratory symptoms rather than sudden onset without fever 8
- The barking cough quality, while characteristic, can also occur in tracheomalacia and habit cough, requiring clinical context for differentiation 6