Croup is a disease caused by viral infection which results in swelling inside the trachea, interferes with normal breathing and hence develops a specific barking cough. It is also known as Laryngotracheobronchitis.
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Croup steeple sign

Image: “AP x-ray of the neck in a child with croup demonstrating the steeple sign; narrowing of the the trachea.” by Frank Gaillard – Own work. License: CC BY-SA 3.0

Pathophysiology of Croup

The viral infection causes infiltration of white blood cells especially histiocytes, neutrophils, plasma cells and lymphocytes which ultimately lead to swelling inside trachea, larynx and large bronchi. When the disease is severe it leads to obstruction of airway and causes turbulent airflow leading to stridor.

Epidemiology of Croup

The mean age group affected by this infection is between 6 months and 5–6 years. Croup affects 15 % of children and 5 % of hospitalized patients. The disease is more prevalent in autumn season and affects 50 % more males than females.


Croup is contagious within the first few days.

Signs and Symptoms of Croup

  • Characteristic barking cough
  • Stridor
  • Fever
  • Hoarseness
  • Coryza
  • Hoovers’s sign (indrawing of chest wall)
  • Agitation

Causes and Diagnosis of Croup

Croup is most commonly caused by virus and less commonly by bacteria. Viral cause occurs in 75 % of cases affected by croup and in most of the cases the cause is parainfluenzae virus type 1 and 2, which is a member of paramyxovirus family. It can also be caused by measles virus, respiratory syncytial virus (RSV) and adenovirus.

Croup caused by bacteria is divided into bacterial tracheitis, laryngotracheobronchitis, laryngeal diphtheria, bacterial tracheitis and laryngotracheobronchopneumonitis.

Corynebacterium diphtheriae causes laryngeal diphtheria while laryngotracheobronchitis, bacterial tracheitis and laryngotracheobronchopneumonitis are due to secondary bacterial growth. The most common bacteria associated with croup is staphylococccus aureus, hemophilus influenza, streptococcus pneumonia and moraxella catarrhalis.

Diagnosis is usually made immediately by listening to the barking nature of cough and stridor. Some doctors may order a lateral neck radiograph to rule out any other cause like peritonsillar abcess. In cases of croup, X-ray usually shows “steeple sign” which is narrowing of upper airway.


Severity can be assessed by Westley score.

Feature Number of points assigned for this feature
0 1 2 3 4 5
Chest wall
None Mild Moderate Severe
Stridor None With
At rest
Cyanosis None With
At rest
Level of
Normal Disoriented
Air entry Normal Decreased Markedly decreased
  • A total score of equal to or less than 2 indicates mild croup and there is no stridor at rest
  • A total score of 3-5 indicates moderate croup
  • A total score of 6-11 indicates severe croup, obvious stridor and obvious chest indrawing
  • A total score of more than or equal to 12 indicates respiratory failure

Treatment of Croup

Epinephrine along with steroids can be given in severe cases. In cases where oxygen saturation is compromised and is below 92 % then immediate oxygen should be given. In case of fever, administration of ibubrofen and acetaminophen usually comforts the child.

In moderate to severe cases administration of nebulised epinephrine may improve the condition immediately within 10–30 minutes. If the patient remains calm and breathing is normal for  2–4 hours after administration then the patient can be discharged and sent home.

Administration of corticosteroids like budesonide and dexamethasone immediately improves the outcome even after one dose. Doses of dexamethasone of 0.15, 0.3 and 0.6 mg/kg are all effective. Other treatments which are helpful include inhalation of humidified air or hot steam.

Secondary bacterial infections can be treated by cefotaxime and vancomycin. Antiviral neuraminidase inhibitors are helpful in severe influenza infection. Plenty of fluids should be given to avoid dehydration.

Prognosis and Complications of Croup

Croup is a self limiting disease usually resolving within a day or two in 80 %of the cases. Death rarely occurs by the disease but if death occurs, it is usually due to cardiac arrest.


  • Pneumonia
  • Pulmonary edema
  • Bacterial tracheitis
  • Cyanosis
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