Introduction
The epidemiology of pre-school wheeze is covered in detail elsewhere in this series. In brief, this is a common problem with few solutions. In the UK, the greatest burden of hospitalisations for wheeze is on children age less than 5 years old [1,2]. Most suffer from recurrent episodic, commonly viral induced attacks (EVW). Most remit over time [3]. Worldwide, preschool wheeze is a problem in all environments [4], which makes it all the more disappointing that we have so few evidence based, personalised treatments
The treatment of preschool wheeze, especially the role of inhaled corticosteroids (ICS), has been be-devilled by the mindless “at what age can asthma be diagnosed?”. Clearly the answer depends on the definition of asthma [5]. The Lancet Asthma Commission cut through this by defining asthma purely clinically, wheeze, chest tightness, breathlessness and sometimes excessive cough [6]. This is because asthma is considered an umbrella term like anaemia (low haemoglobin) and arthritis (hot, painful joints). As with anaemia and arthritis, so with asthma, the next question is, “what sort of asthma has this child got?” with a specific focus on treatable traits [7] (Table 1). Notably, the treatable trait approach should be extended beyond pulmonary disease; description of the detailed management of extrapulmonary and social/environmental treatable traits is outwith the scope of this review. However consideration of these traits is necessary for the holistic management of the child Thus, asthma can be diagnosed at any age if a good history is taken, but the underlying endotype will vary across the life course. In preschool wheeze, the key treatable traits are the presence or otherwise of eosinophilic airway inflammation, bronchodilator responsiveness, and bacterial airway infection. Thus the management approach set out in this review draws on this paradigm to determine treatment options. Preschool is defined as age 2-5 years inclusive. Very little is known about the pathophysiology and management of wheeze in the first year of life [8]. We do know that there is no evidence of airway inflammation in these very young children, even if they are really severely affected, atopic and with documented acute bronchodilator reversibility [9]; it is thus very difficult to justify any prescription of ICS in wheezing babies.