Box 9.2.

Wheezing phenotypes in young children

Phenotype	Presentation	Characteristics
Symptom-based	Episodic	Wheezing occurs during specific time periods Often associated with URTIs Absent between these episodes
	Multi-trigger	Episodic wheeze Can occur between episodes, during sleep, and can be triggered by crying, laughing etc.
Age-based	Early transient	Wheezing starts before the age of 3 years with resolution by the age of 6 years
	Persistent	Wheezing starts before the age of 3 years and continues after the age of 6 years
	Late-onset	Wheezing begun between 3 and 6 years of age

URTI: Upper respiratory tract infection