A severe inflammation and obstruction of the upper airway, croup can occur as acute laryngotracheobronchitis (most common), laryngitis, and acute spasmodic laryngitis. It must always be distinguished from epiglottitis.
Croup is a childhood disease affecting boys more commonly than girls (typically between age 3 months and 3 years) that usually occurs during the winter. Recovery is usually complete.
Croup usually results from a viral infection. Parainfluenza viruses cause two-thirds of such infections; adenoviruses, respiratory syncytial virus (RSV), influenza and measles viruses, and bacteria (pertussis and diphtheria) account for the rest.
Signs and symptoms
The onset of croup usually follows an upper respiratory tract infection. Clinical features include inspiratory stridor, hoarse or muffled vocal sounds, varying degrees of laryngeal obstruction and respiratory distress, and a characteristic sharp, barklike cough. These symptoms may last only a few hours or persist for 1 to 2 days.
As croup progresses, it causes inflammatory edema and, possibly, spasm, which can obstruct the upper airway and severely compromise ventilation. Each form of croup has additional characteristics.
The symptoms of this form of croup seem to worsen at night. Inflammation causes edema of the bronchi and bronchioles and increasingly difficult expiration, which frightens the child. Other characteristic features include fever, diffusely decreased breath sounds, expiratory rhonchi, and scattered crackles.