A small amount of edema in this region can cause significant airway obstruction. Air flowing through this narrowed subglottic area causes stridor. The uncomplicated disease usually wanes in 3-5 days but may persist for as many as 10 days. It is the most common form of airway obstruction or stridor in children aged 6 months to 6 years. The vast majority of children with croup do well.
Morbidity is unusual, and mortality is rare.
The mean age of onset is 18 months. Laryngotracheobronchitis is uncommon in persons older than 6 years. The patient usually has a few days of a mild upper respiratory illness with low grade fever, runny nose, and mild cough. Parents may report worsening symptoms on the second night of the illness. The child is fatigued.