Confusable diagnoses · PANCE / PANRE

Croup vs Epiglottitis

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Croup and Epiglottitis are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Croup vs Epiglottitis at a glance

  • Croup: Viral upper airway infection in young children causing barking cough and stridor.
  • Epiglottitis: Life-threatening supraglottic bacterial infection with risk of complete airway obstruction.

Try two board-style questions on Croup vs Epiglottitis

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Question 1PulmonaryMedium
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.
Question 2PulmonaryMedium
A 5-year-old unvaccinated child presents with 8 hours of high fever, drooling, and severe sore throat. He is anxious, sitting in a tripod position with his neck extended, and has muffled 'hot-potato' voice and inspiratory stridor without a barky cough. He appears toxic and is reluctant to lie down. Blood cultures later grow Haemophilus influenzae type b. Which of the following antibiotics is most appropriate, and by what mechanism does it act?
  • ACeftriaxone, which inhibits bacterial cell wall synthesis
  • BAzithromycin, which inhibits the 50S ribosomal subunit
  • CCiprofloxacin, which inhibits bacterial DNA gyrase
  • DVancomycin, which inhibits DNA-dependent RNA polymerase
Reveal answer & full explanation
Correct answer: A — Ceftriaxone, which inhibits bacterial cell wall synthesis
  • ACeftriaxone, which inhibits bacterial cell wall synthesis✓
  • BAzithromycin, which inhibits the 50S ribosomal subunit
  • CCiprofloxacin, which inhibits bacterial DNA gyrase
  • DVancomycin, which inhibits DNA-dependent RNA polymerase

Why Ceftriaxone, which inhibits bacterial cell wall synthesis is correct

  • This is epiglottitis, and the highest-yield risk factor is absent Hib immunization: routine Hib vaccination dramatically reduced pediatric epiglottitis, so unvaccinated children remain susceptible to invasive Haemophilus influenzae type b, which bacteremically seeds the supraglottic tissue and produces the toxic, drooling, tripod, muffled-voice presentation.
  • After securing the airway, first-line therapy is a third-generation cephalosporin such as ceftriaxone, which acts by binding penicillin-binding proteins to inhibit bacterial cell wall (peptidoglycan) synthesis; this both covers H. influenzae and is correctly paired with its mechanism, making it the answer.

Why the others are wrong

  • Azithromycin, which inhibits the 50S ribosomal subunit — the mechanism statement is accurate (macrolides bind the 50S subunit) but azithromycin is not the drug of choice for invasive Hib epiglottitis.
  • Ciprofloxacin, which inhibits bacterial DNA gyrase — the mechanism is correct for fluoroquinolones, but ciprofloxacin is not first-line here and is avoided in young children when alternatives exist.
  • Vancomycin, which inhibits DNA-dependent RNA polymerase — vancomycin actually inhibits cell wall synthesis (D-Ala-D-Ala binding), not RNA polymerase, so both the drug choice and the stated mechanism are wrong (RNA polymerase inhibition describes rifampin).
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Side-by-side comparison

FeatureCroupEpiglottitis
At a glanceViral upper airway infection in young children causing barking cough and stridor.Life-threatening supraglottic bacterial infection with risk of complete airway obstruction.
Classic presentationProdrome 1-3 days: rhinorrhea, mild fever, cough; Classic triad: barking 'seal-like' cough, hoarseness, inspiratory stridor (worse with agitation, crying); Symptoms often worse at night, improve during day; Mild dyspnea; respiratory distress in severe cases; Inspiratory stridor (audible without stethoscope); Suprasternal, intercostal,…Pediatric 'four D's': dysphagia, drooling, dyspnea, dysphonia, in a toxic-appearing child sitting in tripod position. Always consider in any adult with severe sore throat plus muffled voice or stridor.; Classic adult/pediatric: rapid onset (hours) of severe sore throat, odynophagia, drooling, muffled 'hot potato' voice; Fever, often…
Workup / key labsGenerally clinical diagnosis — no labs required in classic presentation; Severe or atypical cases: viral PCR can identify pathogen; Pulse oximetry to assess oxygenation; Westley croup score (0-17) assesses severity using: level of consciousness, cyanosis, stridor, air entry, retractions; Mild (≤2): no/intermittent stridor; minimal…Clinical suspicion based on presentation + visual confirmation by laryngoscopy in OR or controlled setting (cherry-red, edematous epiglottis).; Defer all blood draws and IV placement in unstable children until airway is secured (agitation can precipitate obstruction); Once airway secured: CBC (leukocytosis), blood cultures, throat…
ImagingImaging usually NOT needed; clinical diagnosis sufficient; AP neck radiograph (if obtained): 'steeple sign' — subglottic narrowing of tracheal air column (insensitive but specific); Lateral neck radiograph to exclude epiglottitis if uncertain (normal in croup)Lateral neck soft-tissue radiograph (if patient stable): 'thumbprint sign' — enlarged, thickened epiglottis; specific but only obtain if it will not delay airway management; DO NOT delay airway intervention for imaging in unstable patient; Direct visualization with flexible fiberoptic laryngoscopy by ENT/anesthesia in controlled setting…
First-line treatmentCalm 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…Secure the airway is the priority — minimize handling, keep child calm with caregiver; Children: take to the OR with anesthesia and ENT; inhalational induction with spontaneous breathing preserved, then laryngoscopy and intubation (IV placement waits until the child is anesthetized), with rigid bronchoscopy or tracheostomy ready as…

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Full outlines

Croup (Laryngotracheobronchitis) Epiglottitis All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.