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Recurrent wheezing affects up to one in three children before the age of six. While the majority outgrow symptoms by school age, a clinically important subset progresses to persistent asthma with measurable airway remodeling. Distinguishing transient viral wheeze from early-onset asthma is therefore one of the most consequential decisions in pediatric primary care. Because spirometry is generally not feasible before age five, clinicians must rely on careful symptom characterization, validated clinical prediction tools, and a structured therapeutic trial.
MATERIALS AND METHODS
We performed a focused review of the 2025 Global Initiative for Asthma (GINA) report, the 2020 NAEPP Focused Updates, and primary studies indexed in PubMed and Scopus between January 2015 and December 2025. Search terms combined "preschool," "wheeze," "asthma," "inhaled corticosteroids," "asthma predictive index," and "exacerbation." Two pediatric reviewers screened 421 records and included 56 publications addressing diagnosis, phenotype classification, or pharmacological management in children aged 1 to 5 years.
Three dominant clinical phenotypes were consistently described. Episodic viral wheeze presents only with respiratory infections and typically remits by age six. Multiple-trigger wheeze occurs both during and between infections and is more often associated with atopy. Early-onset persistent asthma is characterized by symptoms before age three that continue beyond school age and is strongly linked to parental asthma, eczema, and elevated specific IgE.
The modified Asthma Predictive Index (mAPI) requires four or more wheezing episodes in the past year plus one major criterion (parental asthma, atopic dermatitis, or aeroallergen sensitization) or two minor criteria (food allergy, peripheral eosinophilia ≥4 percent, or wheezing apart from colds). A positive mAPI raises the probability of school-age asthma from a baseline of approximately 30 percent to over 70 percent.
Low-dose daily inhaled corticosteroids (ICS) delivered via a spacer with face mask remain the cornerstone of controller therapy for children with persistent symptoms or a positive mAPI. Intermittent high-dose ICS started at the first sign of a viral upper respiratory infection reduces severe exacerbations in the episodic viral wheeze phenotype, although it does not modify long-term natural history. Leukotriene receptor antagonists provide modest symptom control but carry a class warning for neuropsychiatric adverse effects and are now positioned as second-line therapy.
Phenotype-guided care reduces both undertreatment and overtreatment. A child with infrequent episodic viral wheeze and a negative mAPI is unlikely to benefit from chronic ICS and should be managed with as-needed bronchodilators and parental education. Conversely, a child with multiple-trigger wheeze and a positive mAPI warrants a three-month trial of daily low-dose ICS with structured reassessment. Treatment should be stepped down once symptoms have been controlled for at least three months, using the lowest effective dose to minimize growth velocity effects.
Key barriers to optimal care include inhaler technique errors, environmental tobacco smoke exposure, and inconsistent follow-up. Structured parental education, written asthma action plans adapted for preschool children, and routine inhaler technique review at every encounter substantially improve outcomes.
In preschool-aged children, asthma should be approached as a heterogeneous syndrome rather than a single disease. Combining careful clinical phenotyping, validated prediction tools such as the mAPI, and a stepwise pharmacological strategy enables clinicians to target controller therapy to children most likely to benefit while sparing those with self-limited viral wheeze from unnecessary chronic treatment.
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