Episodic viral wheeze and multiple trigger wheeze in preschool children: a useful distinction for clinicians?

Accumulating evidence suggest that splitting preschool recurrent wheezing disorders into Episodic (Viral) Wheeze (EVW) and Multiple Trigger Wheeze (MTW) is an oversimplification. There is little evidence that the EVW and MTW phenotypes are related to the longitudinal patterns of wheeze, or to different underlying pathological processes. As the clinical response to inhaled corticosteroids and montelukast varies considerably between individual children with EVW, and between individual patients with MTW, the clinical usefulness of the EVW-MTW approach is doubtful. Based on the currently available evidence, we propose to describe preschool wheeze symptoms not only in terms of temporal pattern, but also in terms of frequency and severity, and age of onset. Relevant associated clinical parameters like atopy and eczema should be described with recognition of age of onset, pattern, and severity. Comparing these data to biomarkers and histopathology may help to improve our understanding of preschool wheezing disorders in the future. Until phenotypes can be described that are associated with different pathobiological process, are related to different longitudinal outcomes, or are clearly different in terms of response to therapy, clinicians are encouraged to take a trial and error approach of different therapeutic agents in preschool children with troublesome recurrent wheeze.