In a four‑month‑old infant presenting with coarse breath sounds and a seal‑like barky cough, what is the most likely diagnosis and is a single dose of dexamethasone safe?

Diagnosis and Safety of Steroids in a Four-Month-Old with Barky Cough

Your four-month-old has croup (viral laryngotracheobronchitis), and a single dose of oral dexamethasone is both safe and strongly recommended for all children with croup, regardless of severity. 1

Clinical Diagnosis

Croup is diagnosed clinically based on the characteristic barking ("seal-like") cough, which is the hallmark symptom of this viral upper airway infection. 1 The coarse lung sounds you're hearing likely represent upper airway turbulence from laryngeal inflammation and edema. 2, 3

Key diagnostic features in your infant include:

• Barking cough – the pathognomonic sign that allows bedside diagnosis without imaging 1, 4
• Inspiratory stridor (if present) – indicates upper airway narrowing 3, 5
• Hoarseness or change in cry – reflects laryngeal involvement 6, 5
• Low-grade or absent fever – typical of viral croup 3, 6

Imaging is unnecessary and should be avoided unless you suspect an alternative diagnosis such as foreign body aspiration or bacterial tracheitis. 1

Important Age Consideration

At four months old, your infant is younger than the typical croup age range (6 months to 3 years), which warrants closer attention. 3, 5 While croup can occur at this age, if symptoms are severe, persistent, or atypical, flexible bronchoscopy should be considered because up to 68% of infants with stridor have concomitant lower airway abnormalities. 7, 1

Steroid Treatment: Safety and Efficacy

Oral dexamethasone 0.15-0.60 mg/kg as a single dose (maximum 10 mg) is the first-line treatment and should be administered immediately to all children with croup. 1, 4 The evidence supporting steroid safety and efficacy is robust:

• Dexamethasone has transformed croup management over the past decade and is now the cornerstone of treatment. 2, 4
• A single oral dose is highly efficacious in reducing symptom severity, return visits, emergency department visits, and hospital admissions. 4, 5
• Steroids are recommended for ALL cases of croup regardless of severity. 1, 4
• The onset of action is approximately 6 hours, so symptoms may not improve immediately. 3

For infants who cannot tolerate oral medication, nebulized budesonide or intramuscular dexamethasone are reasonable alternatives. 5

When to Escalate Care

Nebulized epinephrine (0.5 ml/kg of 1:1000 solution) should be added if your infant develops:

• Stridor at rest 1
• Respiratory distress (use of accessory muscles, chest wall retractions, tracheal tug) 1
• Agitation (which may signal hypoxemia rather than anxiety) 1, 8
• Oxygen saturation <94% 1

Critical safety point: If nebulized epinephrine is used, your infant must be observed for at least 2 hours after the last dose due to risk of rebound symptoms. 1, 3 The effect of epinephrine is short-lived (1-2 hours) and temporary. 1

Red Flags Requiring Immediate Emergency Evaluation

Seek immediate medical attention if your infant develops:

• Silent chest, cyanosis, or severe fatigue/exhaustion – signs of impending respiratory failure 1
• Inability to feed or signs of dehydration 8
• Oxygen saturation <92% 1, 8
• Respiratory rate >70 breaths/min 1, 8
• Worsening stridor or respiratory distress despite treatment 8

Supportive Care at Home

• Maintain adequate hydration to thin secretions 8
• Use antipyretics (acetaminophen or ibuprofen) for fever control to improve comfort 1, 8
• Minimize handling if your infant appears severely ill, as this reduces oxygen demand 1, 8
• Provide supplemental oxygen if available to maintain oxygen saturation ≥94% 1

What NOT to Do

• Never give over-the-counter cough or cold medications – they provide no benefit and may cause serious harm or death in infants. 8 Between 1969-2006, there were 43 deaths in infants under 1 year associated with decongestants alone. 8
• Do not use topical decongestants in infants under 1 year due to narrow therapeutic margin and risk of cardiovascular/CNS toxicity. 8
• Avoid honey in infants under 1 year (botulism risk) and it doesn't help croup anyway. 1
• Do not rely on humidified air or mist therapy as primary treatment – while maintaining 50% humidity is reasonable, steroids are the evidence-based intervention. 3

Follow-Up

Return to your healthcare provider if symptoms are not improving within 48 hours or if they worsen at any time. 1, 8 If the cough persists beyond 4 weeks, systematic evaluation for chronic cough is warranted, including chest radiograph and assessment for underlying airway abnormalities. 7, 8