Croup, or viral laryngotracheobronchitis, is an acute inflammation of the entire airway, mainly in the glottic and subglottic areas, resulting in airway narrowing, obstruction, and voice loss. Therefore, it has generally been described as a triad of hoarse voice, harsh barking cough, and inspiratory stridor.

Typically, the condition affects younger children (6-36 months), with a peak incidence at 2 years of age. It is the most common cause of acute upper airway obstruction in young children; ˜3% of children experience an episode before 6 years of age.

Seasonal outbreaks have been described in the fall and winter, although it may occur year-round in some areas.

Males are more commonly affected than are females.

Viral infection is the predominant etiology; parainfluenza virus (types 1, 2, and 3) is the most common agent. Other common viral agents are respiratory syncytial virus (RSV) and influenza virus, with less commonly encountered viruses including adenovirus, rhinovirus, enterovirus, and measles virus.

Mycoplasma pneumoniae is one of the few nonviral microorganisms that has been reported as an etiologic agent.

In children, the larynx is very narrow and is composed by the rigid ring of the cricoid cartilage; therefore, a viral infection causing inflammation of this area leads to airway edema and subsequent obstruction. This obstruction results in the classic symptoms of stridor and cough.

Croup usually presents initially with a coryzal prodrome (1-4 days).

Common symptoms include clear rhinorrhea, low-grade temperature, and mild tachypnea followed by barking cough, hoarseness, and stridor.

Obstructive symptoms occur most commonly at night.

Severity of airway narrowing may be determined by the presence of stridor at rest, tachypnea, retractions, tracheal tug, cyanosis, and pallor as well as decreased breath sounds, which indicate critical narrowing.

Epiglottitis represents a true pediatric emergency with acute infectious supraglottic obstruction that may rapidly lead to life-threatening airway obstruction.

It affects children of all ages, with a peak around 3-6 years of age, although its incidence has declined significantly since Haemophilus influenzae type B immunization was introduced in 1998.

H. influenzae type B is the most common cause in children, although its prevalence has markedly decreased in the postvaccine era. Other agents include group A Streptococcus, H. influenzae (types A, F, and nontypeable), Staphylococcus aureus, Candida albicans, and Streptococcus pneumoniae.

Direct invasion by the inciting agent causes inflammation of the epiglottis, aryepiglottic folds, ventricular bands, and arytenoids. Subsequently, there is accumulation of inflammatory cells and edema fluid where the stratified squamous epithelium is loosely adherent to the anterior surface and the superior third of the posterior portion of the epiglottis.

Diffuse infiltration with polymorphonuclear leukocytes, hemorrhage, edema, and fibrin deposition occurs. Microabscesses may form. As the edema increases, the epiglottis curls posteriorly and inferiorly. This causes airway obstruction.

Inspiration tends to draw the inflamed supraglottic ring into the laryngeal inlet.

Epiglottitis is a rapidly progressing illness in previously healthy individuals. Patients are usually anxious and toxic appearing and assume the classic “tripod position” (forward-leaning posture with bracing arms and extension of the neck that allows for maximal air entry).

Other symptoms typically present are high fever, muffled or absent voice (“hot potato”), sore throat, drooling, inspiratory stridor, dysphagia, protruded jaw, and extended neck.

This acute bacterial infection of the trachea often also involves the larynx and bronchi. It has been called bacterial laryngotracheobronchitis and pseudomembranous croup.

A cause of acute airway obstruction, this condition may potentially be life threatening.

Most patients are <3 years of age (usually 3 months to 2 years), although older children may be affected. There are no clear sex differences in incidence or severity.

There seems to be no seasonal preferences.

The most common cause is S. aureus, but other encountered agents are S. pneumoniae, S. pyogenes, Moraxella catarrhalis, and H. influenzae. Anaerobic organisms have also been reported.

Invasion of opportunistic bacterial organisms, often following an upper airway viral infection, causes subglottic edema with ulcerations, copious and purulent secretions, and pseudomembrane formation.

The typical presentation involves a history of an upper respiratory infection (URI) for ˜3 days characterized by a low-grade fever and a “brassy” cough. The illness then evolves rapidly with high fever and signs of airway obstruction, including stridor, cough, drooling, and supine positioning (preference to lie flat).

Patients generally appear toxic.

There is also evidence of purulent airway secretions.

This accidental ingestion occurs commonly in children <5 years of age but has been described at any age.

Younger children are typically at higher risk because of oral exploration and immaturity of their swallowing functions.

This situation may be life threatening; it is the leading cause of accidental death by ingestion in younger children.

Ingested food and toy parts are aspirated into the airways, causing choking.

The foreign particle provokes localized airway inflammation with mucosal edema, inflammation, and development of granulation tissue. Atelectasis of the area involved and empyema may occur.