Croup (Laryngotracheobronchitis)



  • Croup (laryngotracheobronchitis) is a common respiratory illness in children that presents with hoarseness, a characteristic barking cough, rhinorrhea, and fever.
  • Spasmodic croup (subglottic allergic edema) refers to an illness characterized by sudden inspiratory stridor at night followed by sudden resolution. Mild cold symptoms may be present but are often absent. The child can have frequent attacks on the same night or for multiple, successive nights.


  • Accounts for 3–5% of total visits to the emergency department (ED)
  • Most commonly occurs in children between 6 and 36 months of age
    • Although cases can be seen up to 6 years of age, it is uncommon in children >6 years.
    • Mean age at presentation is 18 months.
  • Timing
    • Most prevalent in the fall to early winter
    • Major peak in October with parainfluenza type 1, with minor peaks later during respiratory syncytial virus (RSV) and influenza season
    • ED visits for croup are most frequent between the hours of 10 p.m. and 4 a.m.
  • More common in males (ratio 1.4:1)

Risk Factors

  • Anatomic narrowing of the airway such as in subglottic stenosis or laryngeal cysts or hemangiomas
  • Prior history of croup
  • Hyperactive airway triggered by atopy or reflux seen in recurrent croup
  • Preexisting airway swelling


  • In children, the cricoid ring of the trachea, located in the immediate subglottic area, is the narrowest part of their upper airway. A small amount of edema in this region can lead to significant airway obstruction, which is what makes children especially susceptible to this illness.
  • Caused mainly by respiratory viruses including the following:
    • Parainfluenza virus types 1 to 3, most commonly; accounting for 65% of cases
    • Adenovirus
    • RSV—in some cases, patients may also have wheezing present
    • Influenza virus A, B
    • Rhinoviruses
    • Enteroviruses
    • Metapneumovirus
    • Enteric cytopathogenic human orphan virus (echovirus)
    • Human coronavirus NL63
    • Measles—in areas where measles is prevalent
    • Mycoplasma pneumoniae—associated with mild cases of croup
    • Bacterial infection may occur secondarily by Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus pneumoniae.

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