A 4‑year‑5‑month‑old child with a two‑week history of persistent, intense cough that worsens with exercise and early morning, without fever or rhinorrhea, and unresponsive to 15 mg daily dextromethorphan, what is the most likely diagnosis and appropriate management?

Most Likely Diagnosis: Exercise-Induced Bronchoconstriction or Early Asthma

This 4.5-year-old child with a 2-week persistent dry cough that worsens with physical activity and upon waking, unresponsive to dextromethorphan and without fever or rhinorrhea, most likely has exercise-induced bronchoconstriction or early asthma, and should receive a trial of inhaled corticosteroids (budesonide 0.25–0.5 mg twice daily via nebulizer) for 2–4 weeks with mandatory reassessment. 1, 2

Why Dextromethorphan Failed

• Dextromethorphan has no proven efficacy in children for cough relief and should not be used in this age group. 1, 2, 3
• Over-the-counter cough suppressants lack evidence of benefit in pediatric populations and do not address underlying airway inflammation. 1, 2
• The child's lack of response to dextromethorphan is expected and does not indicate treatment failure—it indicates the wrong medication was chosen. 1, 2

Key Clinical Features Pointing to Asthma

• Cough triggered by physical activity is a hallmark of exercise-induced bronchoconstriction, a common asthma presentation in young children. 2, 3
• Early-morning cough (immediately upon waking) is characteristic of nocturnal airway inflammation seen in asthma. 2, 3
• The absence of fever and rhinorrhea makes ongoing viral infection or sinusitis unlikely. 1, 2
• At 2 weeks duration, this is still classified as acute cough (not yet chronic at 4 weeks), but the exercise and morning pattern strongly suggests reactive airway disease rather than post-viral cough. 1, 2

Immediate Management Plan

Step 1: Initiate Inhaled Corticosteroid Trial (2–4 Weeks)

• Prescribe budesonide inhalation suspension 0.25 mg twice daily via nebulizer (or equivalent beclomethasone 400 mcg/day). 1, 4
• This dose is effective for most childhood asthma and minimizes adverse effects compared to higher doses. 1, 4
• Explain to parents that symptom improvement may begin within 2–8 days, but maximum benefit requires 4–6 weeks of treatment. 4
• Schedule mandatory follow-up at 2–4 weeks to assess response; do not continue medication beyond this period if no improvement occurs. 1, 2

Step 2: Environmental Modifications

• Eliminate all environmental tobacco smoke exposure immediately—this is a critical modifiable risk factor that worsens cough and impairs treatment response. 1, 2, 3
• Minimize exposure to other respiratory irritants (dust, strong odors, cold air during exercise). 1, 2, 3

Step 3: Supportive Measures

• Ensure adequate hydration to thin respiratory secretions. 2, 3, 5
• Advise an upright sleeping position; avoid lying flat, which reduces cough effectiveness. 2, 3, 5
• Do not use honey in this age group for symptomatic relief (honey is recommended only for children older than 1 year, but evidence is strongest in older children). 2

Critical Reassessment at 2–4 Weeks

If Cough Resolves with Inhaled Corticosteroids:

• Do not automatically diagnose asthma—resolution may represent spontaneous improvement (period effect) or a transient response to inhaled corticosteroids. 1
• Taper and discontinue the inhaled corticosteroid after 2–4 weeks and observe for recurrence. 1
• If cough recurs upon stopping medication and resolves again with reinitiation, this supports a diagnosis of asthma. 1, 6
• If cough does not recur, the child likely had a self-limited post-viral reactive airway process, not chronic asthma. 1

If Cough Persists Despite Inhaled Corticosteroids:

• Do not increase the inhaled corticosteroid dose—cough unresponsive to standard-dose inhaled corticosteroids is unlikely to respond to higher doses. 1
• Stop the inhaled corticosteroid and proceed to chronic cough evaluation (see below). 1

If Cough Becomes Wet/Productive:

• Initiate a 2-week course of antibiotics (amoxicillin or amoxicillin-clavulanate) targeting common respiratory bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis). 1, 2, 3
• This suggests protracted bacterial bronchitis rather than asthma. 1, 2, 3

Evaluation at 4 Weeks (If Cough Persists)

• At 4 weeks, the cough is classified as chronic and warrants systematic investigation. 1, 2, 3
• Obtain a chest radiograph to exclude structural abnormalities, pneumonia, foreign body, or bronchiectasis. 1, 2, 3
• Perform spirometry with pre- and post-bronchodilator testing if the child can cooperate (most 4.5-year-olds cannot perform reliable spirometry; defer until age 6–7 years if needed). 1, 2, 3
• Re-classify the cough as wet/productive versus dry to guide further management. 1, 2, 3

If Dry Cough Persists at 4 Weeks:

• Consider asthma only if additional features are present: recurrent wheeze, nocturnal symptoms beyond cough alone, documented reversible airflow obstruction on spirometry, or family history of atopy. 1, 2, 3
• Evaluate less common etiologies: tracheomalacia (expiratory wheeze worsening with crying), habit cough (disappears during sleep), or functional disorders. 1, 3
• Do not diagnose asthma based on isolated cough alone—the majority of children with chronic isolated cough lack asthma-related airway inflammation. 1, 2, 3, 7, 6

If Wet Cough Develops or Persists at 4 Weeks:

• Prescribe a 2-week course of antibiotics targeting common respiratory bacteria. 1, 2, 3
• If wet cough persists after the initial 2-week course, extend antibiotics for an additional 2 weeks. 1, 2, 3
• If wet cough persists after a total of 4 weeks of antibiotics, refer for flexible bronchoscopy with quantitative cultures and chest CT to evaluate for bronchiectasis, aspiration, cystic fibrosis, or immunodeficiency. 1, 2, 3

Red Flags Requiring Immediate Evaluation

• Respiratory distress (respiratory rate > 50 breaths/min, use of accessory muscles, oxygen saturation < 92%). 2, 3, 5
• Paroxysmal cough with post-tussive vomiting or inspiratory "whoop"—suspect pertussis and obtain nasopharyngeal culture. 1, 2, 3
• Cough with feeding—suggests aspiration and requires swallow study. 1, 2, 3
• Digital clubbing—indicates chronic lung disease (bronchiectasis, cystic fibrosis). 1, 2, 3
• Failure to thrive or hemoptysis—warrants immediate pulmonology referral. 1, 2, 3
• High fever ≥ 39°C (102.2°F)—suggests serious bacterial infection. 2, 3, 5

Common Pitfalls to Avoid

• Over-diagnosing asthma based solely on cough is the most frequent error in pediatric practice. 1, 2, 3, 7, 6
• Avoid the term "cough-variant asthma" in children—this diagnosis should be reserved for older children with documented variable airflow obstruction and bronchodilator response. 1, 2, 6
• Do not prescribe empirical GERD therapy (proton pump inhibitors) without gastrointestinal symptoms (regurgitation, heartburn, epigastric pain)—GERD is not a common cause of chronic cough in children. 1, 2, 3
• Do not prescribe antihistamines or decongestants—these have no proven benefit for cough in children and carry risk of adverse effects. 1, 2, 3, 5
• Do not prescribe antibiotics for dry cough—antibiotics are indicated only for chronic wet/productive cough. 1, 2, 3
• Therapeutic trials must be time-limited (2–4 weeks maximum)—medications should be discontinued if no clear benefit is demonstrated. 1, 2

Parent Education and Expectations

• Explain that the exercise and morning cough pattern suggests reactive airways, which may represent early asthma or a transient post-viral process. 2, 3
• Reassure parents that the inhaled corticosteroid trial is diagnostic as well as therapeutic—response to treatment helps confirm the diagnosis. 1, 6
• Emphasize that most childhood coughs resolve spontaneously within 1–3 weeks, and 90% are cough-free by day 21. 2, 3, 5
• Provide clear instructions on warning signs requiring immediate return: respiratory distress, new fever, inability to feed, or paroxysmal cough with vomiting. 2, 3, 5
• Address parental concerns directly—anxiety about cough often drives inappropriate medication use. 1, 2, 3