# Croup

> Croup for NEET-PG Paediatrics: parainfluenza stridor, barking cough, steeple sign, dexamethasone and nebulised adrenaline in exam notes.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/croup
- Exam / course: NEET-PG · Subject: Paediatrics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Croup", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/croup

## 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.