Viral upper airway infection in young children causing barking cough and stridor.
Also known as: croup, laryngotracheobronchitis, viral croup, spasmodic croup
Overview
Acute viral upper airway infection involving the larynx, trachea, and bronchi (laryngotracheobronchitis), causing subglottic inflammation and edema with the characteristic barking cough, hoarseness, and inspiratory stridor in young children.
Epidemiology
Most common cause of acute upper airway obstruction in children. Peak age 6 months to 3 years (rare after age 6). Boys > girls (~1.5:1). Highest incidence in fall and winter.
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Question 1PulmonaryMedium
A 3-year-old has a barky cough, inspiratory stridor only when agitated, and hoarseness after 2 days of rhinorrhea. He is not drooling and appears nontoxic. Which of the following is the most appropriate treatment?
ANebulized racemic epinephrine
BNebulized albuterol treatments
COral amoxicillin therapy
DSingle-dose oral dexamethasone
Reveal answer & full explanation
Correct answer: D — Single-dose oral dexamethasone
ANebulized racemic epinephrine
BNebulized albuterol treatments
COral amoxicillin therapy
DSingle-dose oral dexamethasone✓
Why Single-dose oral dexamethasone is correct
Croup is viral subglottic inflammation; a single dose of dexamethasone reduces edema and is recommended across all severity levels.
It shortens symptoms, decreases return visits, and lowers the need for further intervention.
This child has mild croup (stridor only with agitation, nontoxic), so dexamethasone alone is appropriate; nebulized epinephrine is added for stridor at rest or moderate-to-severe distress.
Why the others are wrong
Nebulized racemic epinephrine — Reserved for stridor at rest or moderate-to-severe distress; this child has stridor only with agitation, so steroid therapy alone is sufficient and epinephrine adds rebound and observation burden.
Oral amoxicillin therapy — Croup is viral, so antibiotics provide no benefit (antibiotic-reflex trap).
Nebulized albuterol treatments — Albuterol relaxes lower-airway smooth muscle and does nothing for fixed subglottic edema (misapplied wheeze therapy).
Question 2PulmonaryMedium
A 2-year-old boy is brought to the emergency department in the early morning with a 2-day history of rhinorrhea and low-grade fever followed by a barking cough and a hoarse cry. On exam he is alert and non-toxic, sitting comfortably in his mother's lap with audible inspiratory stridor that worsens when he cries. There is no drooling and he is handling secretions normally. Vital signs show a temperature of 38.0 C (100.4 F), heart rate of 130/min, and oxygen saturation of 97 percent on room air. Neck and chest radiographs are obtained. Which of the following radiographic findings best supports the most likely diagnosis?
ASubglottic narrowing of the air column
BWidened prevertebral soft-tissue space
CHyperinflation of a single lung field
DSwollen, thumb-shaped epiglottic shadow
Reveal answer & full explanation
Correct answer: A — Subglottic narrowing of the air column
ASubglottic narrowing of the air column✓
BWidened prevertebral soft-tissue space
CHyperinflation of a single lung field
DSwollen, thumb-shaped epiglottic shadow
Why Subglottic narrowing of the air column is correct
The vignette is classic croup (laryngotracheobronchitis): viral prodrome, barking cough, hoarseness, and inspiratory stridor in a non-toxic toddler, worse with agitation.
Viral edema of the subglottic larynx narrows the tracheal air column, producing the "steeple sign" on an AP neck radiograph — a tapered, pencil-point narrowing just below the vocal cords.
This sign is specific but insensitive; croup remains a clinical diagnosis, so imaging is reserved for atypical or uncertain presentations.
Why the others are wrong
Swollen, thumb-shaped epiglottic shadow — the thumbprint sign signals epiglottitis, which presents with high fever, a toxic-appearing drooling child in tripod posture, and no barking cough; this child is non-toxic with a barking cough.
Widened prevertebral soft-tissue space — points to retropharyngeal abscess, which causes neck stiffness, fever, and drooling rather than a viral prodrome with a barking cough.
Hyperinflation of a single lung field — a finding of foreign body aspiration, suggested by a sudden choking episode with focal wheeze, not a multi-day viral prodrome with stridor.
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Anatomic subglottic narrowing (any child) — small change in radius dramatically increases resistance
Pathophysiology
Viral infection of upper airway mucosa → inflammation and edema of subglottic larynx and trachea → narrowing of the cricoid ring (narrowest part of pediatric airway) → turbulent airflow producing inspiratory stridor and barking cough. Parainfluenza virus types 1-3 cause ~75% of cases (type 1 most common); RSV, influenza, adenovirus, SARS-CoV-2 also implicated.
Mild dyspnea; respiratory distress in severe cases
Signs / physical exam
Inspiratory stridor (audible without stethoscope)
Suprasternal, intercostal, or subcostal retractions in moderate-severe disease
Hoarse voice, barking cough
Tachypnea, mild hypoxia in severe cases (rare)
Generally non-toxic appearance (distinguishes from epiglottitis)
Differential diagnosis
Epiglottitis — High fever, toxic appearance, drooling, tripod posture, NO cough; thumbprint sign on lateral neck XR; airway emergency
Bacterial tracheitis — High fever, toxic appearance, thick purulent secretions, less responsive to standard croup therapy; staphylococcal/streptococcal; airway intervention often needed
Foreign body aspiration — Sudden choking episode, focal wheeze or stridor; CXR may show unilateral hyperinflation
Westley croup score and matched management approach.
Treatment
First-line
Calm child — avoid agitation (worsens stridor); allow caregiver to hold
Humidified air or mist tents — historically used but lack evidence; comfort measure
Single-dose oral, IM, or IV dexamethasone 0.6 mg/kg (max 16 mg) — first-line for ALL severities (including mild); reduces ED return, duration, and admissions
Alternative oral steroid: prednisolone (less commonly used; shorter half-life)
Nebulized budesonide if unable to tolerate PO dexamethasone (equivalent efficacy)
Moderate-severe disease: ADD nebulized racemic epinephrine 0.5 mL of 2.25% in 2.5 mL NS (or L-epinephrine 5 mL of 1:1000) — rapid airway edema reduction
Observe ≥3-4 hours after nebulized epinephrine (rebound stridor); discharge if no stridor at rest and air entry normal
Supplemental oxygen if hypoxic (uncommon in croup)
Second-line / adjunct
Heliox (helium-oxygen mixture) — controversial; reserved for severe refractory cases
Intubation rarely required (<1%) — use smaller endotracheal tube than expected for age due to subglottic edema
Admit if: persistent stridor at rest after treatment, multiple epinephrine doses, dehydration, social concerns, age <6 months
Antibiotics ONLY if bacterial tracheitis or superimposed infection suspected (NOT for routine croup)
Complications
Respiratory failure requiring intubation (rare with appropriate treatment)
Bacterial tracheitis (rare but life-threatening — high fever, toxic, thick secretions)
Post-extubation subglottic stenosis (if intubated and traumatic)
Single-dose dexamethasone 0.6 mg/kg (max 16 mg) is first-line for ALL severities of croup — even mild — and has been the most impactful change in management.
Spasmodic croup: sudden-onset nocturnal stridor without preceding URI symptoms; often allergic/atopic; managed similarly.
Always observe ≥3-4 h after nebulized epinephrine for rebound stridor before discharge.
Croup-like presentation with fever and toxic appearance — think bacterial tracheitis, epiglottitis, or retropharyngeal abscess.
Steeple sign on AP neck XR is specific but insensitive; clinical diagnosis is sufficient.
References
Cochrane Croup — Glucocorticoids for Croup in Children (Gates et al., Cochrane Database Syst Rev 2018)
Pediatrics 2022 — Diagnosis and Management of Croup (Bjornson and Johnson, Pediatrics 2022)
Westley Score — Nebulized Racemic Epinephrine by IPPB for the Treatment of Croup (Westley et al., Am J Dis Child 1978)
NEJM Review — Croup (Bjornson and Johnson, NEJM 2008)
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