Croup is a group of respiratory diseases that often affect infants and children under age 6. It is characterized by a barking cough; a whistling, obstructive sound (stridor) as the child breathes in; and hoarseness due to obstruction in the region of the larynx. It may be mild, moderate or severe, and severe cases, with breathing difficulty, can be fatal if not treated in a hospital.

Presentation

Croup affects 5% of children in the second year of life; the peak incidence is between 7 and 36 months. The group of respiratory diseases consists of spasmotic croup, acute laryngotracheitis, laryngotracheobronchitis (LTB), laryngotracheobronchopneumitis (LTBP), and laryngeal diphtheria. LTB and LTBP, which usually involve a bacterial infection, are usually severe.

The first step in diagnosis is to exclude other acute obstructive illnesses in the region of the larynx, such as epiglottitis, a foreign body, or angioneurotic edema of the epiglottis. Misdiagnosing an obstructive airway disease can be fatal.

Signs and symptoms

Croup is characterized by a harsh "barking" cough and sneeze, inspiratory stridor (a high-pitched sound heard on inhalation), nausea/vomiting, and fever. Hoarseness is usually present. More severe cases will have respiratory distress.

The "barking" cough (often described as a "seal like bark") of croup is diagnostic. Stridor will be provoked or worsened by agitation or crying. If stridor is also heard when the child is calm, critical narrowing of the airway may be imminent.

In diagnosing croup, it is important for the physician to consider and exclude other causes of shortness of breath and stridor, such as foreign body aspiration and epiglottitis.

On a frontal X-ray of the C-spine, the steeple sign suggests the diagnosis of croup.

Causes

Croup is most often caused by parainfluenza virus, primarily types 1 and 2 (some definitions limit the term "croup" to this pathogen). However, other viral and possibly bacterial infections can also cause it. It is most common in the fall and winter but can occur year-round, with a slight predilection for males.

The respiratory distress is caused by the inflammatory response to the infection, rather than by the infection itself. It usually occurs in young children as their airways are smaller and differently shaped than adults', making them more susceptible. There is some element of genetic predisposition as children in some families are more susceptible than others.

An entity known as spasmodic croup also occurs, distinct from the infectious variety, due to laryngeal spasms.

Treatment

The Alberta Clinical Practice Guideline Working Group has developed guidelines for diagnosing and treating croup, including a scoring system for classifying severity. The severe form (which affected less than 1% of children seen in the emergency department) involves breathing difficulties, indicated by stridor, chest retractions, agitation and distress. Lethargy or decreased level of consciousness is a sign of impending respiratory failure, and requires emergency medical treatment. LTB and LTBP are usually severe, and require treatment in the intensive care unit, with a endotracheal (ET) tube to assist breathing, and antibiotics.