Croup
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Direct answer
Croup (acute laryngotracheobronchitis) is viral inflammation and oedema of the subglottic airway — the narrowest point of a young child's larynx — produced most often by parainfluenza viruses in children between six months and three years. The classic picture is a barky, seal-like cough with inspiratory stridor, hoarseness and low-grade fever, characteristically worse at night after a coryzal prodrome. A single dose of oral dexamethasone (or nebulised budesonide) is given at every severity, with nebulised adrenaline added for stridor at rest; the steeple sign on a neck radiograph is the classic examination finding.
What you must remember
- Cause and age: parainfluenza virus types 1 and 2 lead (also type 3, respiratory syncytial virus, influenza, adenovirus); six months to three years, in autumn and winter.
- Clinical triad: barking cough, inspiratory stridor and hoarseness, worse at night after two days of coryza; the child is usually not toxic.
- Pathology: oedema of the subglottic cricoid region — the only complete cartilage ring of the airway — where a millimetre of swelling narrows the infant airway dramatically.
- Steroid for everyone: a single oral dose of dexamethasone 0.15-0.6 mg/kg (or nebulised budesonide) in all cases, including mild ones — the most testable management fact.
- Nebulised adrenaline: for stridor at rest or severe distress — 1:1000 adrenaline at 0.5 mL/kg up to 5 mL nebulised — with observation afterwards for rebound obstruction.
- Radiograph: the steeple sign, tapering of the subglottic air column on the anteroposterior neck view — classic, though imaging is rarely needed.
- Stridor differentials: epiglottitis (toxic, drooling, tripod posture, thumb sign, no barking cough — do not examine the throat; secure the airway), bacterial tracheitis (staphylococcal, toxic, poor response to croup therapy) and inhaled foreign body (sudden choking, unilateral signs).
Common confusion
Croup against epiglottitis is the eternal comparison: croup is viral, subglottic, preceded by coryza, with barky cough and hoarseness in a well-looking child; epiglottitis is bacterial (classically Haemophilus influenzae type b), supraglottic and abrupt, with high fever, drooling, muffled voice, tripod sitting and a thumb-print sign — and its first step is airway protection in theatre, never a throat examination. The second confusion is spasmodic croup: the recurrent, atopic child who wakes suddenly at night with stridor and minimal fever, resolving within hours.
Exam-focused takeaway
NEET-PG tests croup on drug choice, sign naming and differential diagnosis. Single-dose dexamethasone appears as "drug of choice" and as "which drug is given even in mild disease". The steeple and thumb signs are the radiology pair, and the croup-versus-epiglottitis columns feed matching questions. Know the adrenaline recipe and its observation requirement, and the warning that a toxic, drooling or non-responding "croup" child may have bacterial tracheitis needing airway readiness plus staphylococcal cover.
Frequently asked questions
Which virus most commonly causes croup?
Parainfluenza virus, types 1 and 2 above all, with respiratory syncytial virus, influenza and adenovirus as other causes.
What is the drug of choice?
A single dose of oral dexamethasone 0.15-0.6 mg/kg (or nebulised budesonide) — given at every severity, including mild cases.
When is nebulised adrenaline used?
For stridor at rest or severe distress — 1:1000 adrenaline at 0.5 mL/kg up to 5 mL nebulised — with the child observed for rebound.
What is the steeple sign?
Tapering, pencil-point narrowing of the subglottic air column on an anteroposterior neck radiograph — the classic imaging sign of croup.
How does croup differ from epiglottitis?
Croup is viral, subglottic and barky in a well child; epiglottitis is bacterial, supraglottic and toxic with drooling and tripod posture, managed by immediate airway protection without throat examination.