Introduction
Wheezing is a common symptom in preschool children due to small airway size and frequent viral infections.
To better characterize wheezing phenotypes in early childhood, the European Respiratory Society (ERS) task force proposed two main categories:
- Episodic (viral) wheeze (EVW)
- Multi-trigger wheeze (MTW)
These terms help predict prognosis and guide management.
1. Episodic (Viral) Wheeze (EVW)
Definition
Wheeze that occurs only during discrete viral respiratory infections, with no symptoms in between episodes.
Age Group
- Common in 1-5 years (preschool).
- Often resolves by school age.
Typical Clinical Features
| Feature | Description |
|---|---|
| Trigger | Exclusively viral URTI (rhinovirus, RSV, etc.) |
| Interval Symptoms | None – child is asymptomatic between episodes |
| Atopy | Usually absent |
| Family history | Often negative for asthma/allergy |
| Night-time cough/wheeze without cold | Absent |
| Response to bronchodilator | Variable, sometimes good |
| Response to inhaled corticosteroids (ICS) | Poor to moderate (benefit only during acute episodes) |
Pathophysiology
- Due to viral-induced airway inflammation and narrowing.
- No persistent airway inflammation like in asthma.
Prognosis
- Usually outgrows by 6 years as airway caliber increases.
- Only a small fraction progress to asthma.
2. Multi-Trigger Wheeze (MTW)
Definition
Wheeze that occurs not only with viral infections but also with other triggers such as allergens, exercise, laughter, crying, or exposure to smoke.
Age Group
- May start in preschool years but often persists into school age.
Typical Clinical Features
| Feature | Description |
|---|---|
| Trigger | Viral + non-viral (exercise, allergens, smoke, crying, etc.) |
| Interval Symptoms | Present even between viral infections |
| Atopy | Common |
| Family history | Often positive for asthma/allergy |
| Night-time cough/wheeze | Common |
| Response to bronchodilator | Good |
| Response to ICS | Good (similar to asthma) |
Pathophysiology
- Reflects persistent airway inflammation and hyper-responsiveness, similar to asthma.
- Considered an early asthma phenotype.
Prognosis
- High risk of developing persistent asthma later in life.
Comparison Table
| Feature | Episodic (Viral) Wheeze | Multi-Trigger Wheeze |
|---|---|---|
| Between episodes | No symptoms | Symptoms persist |
| Triggers | Viral infections only | Viral + other (exercise, allergens, smoke, etc.) |
| Family/atopy history | Usually absent | Often present |
| Night symptoms | Absent | Present |
| Response to ICS | Poor/limited | Good |
| Prognosis | Resolves by school age | Often persists (asthma risk) |
Investigations (for exam answers)
Usually clinical diagnosis based on history.
But if evaluation is needed:
- Spirometry: Often normal between attacks in EVW; reversible obstruction in MTW.
- Allergy testing: Negative in EVW, positive in MTW.
- Fractional exhaled nitric oxide (FeNO): Higher in MTW (marker of eosinophilic inflammation).
Management
| Step | Episodic Wheeze | Multi-Trigger Wheeze |
|---|---|---|
| Acute episode | SABA (salbutamol) and/or oral steroid (short course) | SABA and/or oral steroid |
| Controller therapy | ICS intermittent during viral illness; daily ICS not recommended | Daily low-dose ICS (preventer) + as-needed SABA |
| Other options | Montelukast may reduce episode frequency | Montelukast may help but less effective than ICS |
| Follow-up | Reassess after 6-12 months | Step up/down therapy as per asthma guidelines |
Key Take-Home for Exam
- Episodic (viral) wheeze = no symptoms between episodes.
- Multi-trigger wheeze = symptoms triggered by multiple factors and persistent between colds.
- Multi-trigger = closer to asthma phenotype.
- ICS helpful only in multi-trigger type.
- Most episodic wheezers outgrow symptoms by 6 years.
MCQs for Practice
1. A 3-year-old boy has recurrent wheezing episodes associated only with colds. Between episodes, he is symptom-free. The most likely diagnosis is:
A. Bronchial asthma
B. Episodic (viral) wheeze
C. Multi-trigger wheeze
D. Reactive airway disease
Answer: B – Episodic (viral) wheeze
2. Which of the following features favors multi-trigger wheeze?
A. No symptoms between viral infections
B. Absence of family history of atopy
C. Night-time cough in absence of cold
D. Poor response to inhaled corticosteroids
Answer: C – Night-time cough in absence of cold
3. The typical age for onset of episodic viral wheeze is:
A. Neonatal period
B. 6 months – 5 years
C. After 10 years
D. Adulthood
Answer: B – 6 months to 5 years
4. Most preschool children with episodic viral wheeze:
A. Progress to asthma
B. Develop COPD later
C. Outgrow symptoms by 6 years
D. Have severe atopy
Answer: C – Outgrow symptoms by 6 years
5. Which of the following statements is TRUE regarding multi-trigger wheeze?
A. Symptoms occur only during viral infections
B. Often associated with atopy and family history of asthma
C. No response to bronchodilator
D. Resolves completely by 2 years
Answer: B – Associated with atopy and family history
Viva Questions & Model Answers
Q1. What is the most common cause of wheeze in preschool children?
Viral infection-induced wheeze (episodic wheeze).
Q2. How do you differentiate episodic wheeze from asthma in a 4-year-old?
Episodic wheeze: symptoms only during viral infection, asymptomatic between episodes; Asthma (multi-trigger): symptoms even without infection, with triggers like exercise and night cough.
Q3. What is the management difference between episodic and multi-trigger wheeze?
Episodic: intermittent therapy during viral illness; Multi-trigger: daily controller (ICS).
Q4. What is the role of Montelukast in preschool wheezers?
Can reduce frequency/severity of viral-induced episodes, but benefit modest.
Q5. What is the long-term outcome of each phenotype?
Episodic: often resolves by 6 years; Multi-trigger: may progress to asthma.
Summary Points for Rapid Revision
- Episodic wheeze = viral-only, Multi-trigger = viral + others
- No interval symptoms – Episodic
- Interval symptoms – Multi-trigger
- Atopy & night symptoms – Multi-trigger
- ICS helps only in multi-trigger
- Prognosis better in episodic type
