Croup (Laryngotracheobronchitis)

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Basics

Croup (laryngotracheobronchitis [LBT]) is a self-limited upper respiratory infection causing inflammation and obstructions that presents with barking cough and inspiratory stridor.

Description

  • The term croup is used to refer to viral laryngotracheitis or LBT. It is a common viral illness presenting with nonspecific upper respiratory symptoms such as coryza, cough, and rhinorrhea.
  • Croup causes upper airway inflammation and obstruction leading to pathognomonic barking cough and inspiratory stridor; symptoms start gradually and are worse at nighttime. Other symptoms are skin rash, conjunctivitis, and lymphadenopathies.

Epidemiology

  • Croup is typically self-limited and it affects approximately 3% of children 6 months to 3 years of age with a peak around the 2nd year of life.
  • The vast majority are considered mild cases; however, croup accounts for 5% of annual hospitalization.
  • Less than 3% require intubation.
  • Predominant sex: male > female (1.5:1)

Incidence
  • Six cases per year per 100 children <6 years old.
  • 15% of emergency department visits for upper respiratory disease in children
  • 1.5–6% of cases require hospitalization.
  • <3% of those require intubation.
  • 60% of barking cough resolved within 48 hours and only 2% have symptoms persisting for longer than five nights.

Etiology and Pathophysiology

  • Subglottic region/larynx is entirely encircled by the cricoid cartilage.
  • Inflammatory edema and subglottic mucus production decrease airway radius.
  • Small children have small airways with more compliant walls.
  • Negative-pressure inspiration pulls airway walls closer together.
  • The anatomically small airway is more susceptible to compromise and narrowing caused by the combined edema, mucus secretions, and increased compliance. Small decrease in airway radius causes significant increase in resistance (Poiseuille law: resistance proportional to 1/radius4).
  • Typically caused by viruses that initially infect oropharyngeal mucosa and then migrate inferiorly
  • Parainfluenza virus is the most common pathogen, responsible for over 75% of cases.
    • Type 1 is the most common, causing 18% of all cases of croup.
    • Type 3 is associated with severe illness.
    • Types 2 and 4 are also common.
  • Other viruses: RSV, paramyxovirus, influenza virus type A or B, adenovirus, rhinovirus, enteroviruses (coxsackie and echo), reovirus, measles virus where vaccination not common, and metapneumovirus
  • Haemophilus influenzae type B now rare with routine immunization
  • Mycoplasma pneumoniae and diphtheria have been reported.
  • Measles has been rarely reported in patients with croup in populations inadequately vaccinated.

Genetics
Noncontributory except in those with acquired immunodeficiencies who are at higher risk

Risk Factors

Prior intubations, prematurity, and age <3 years increase the risks for recurrent croup (more than two episodes per year).

General Prevention

Croup spreads through droplets. Children should be considered contagious up to 3 days after the start of illness and/or until afebrile. There is not a specific vaccine for croup, but seasonal influenza vaccine may contribute to decreased risk.

Commonly Associated Conditions

  • If recurrent (>2 episodes in a year) or during first 90 days of life, consider host factors or allergic factors
  • Underlying anatomic abnormality (e.g., subglottic stenosis)
  • Paradoxical vocal cord dysfunction
  • Gastroesophageal reflux disease
  • Neonatal intubation

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Basics

Croup (laryngotracheobronchitis [LBT]) is a self-limited upper respiratory infection causing inflammation and obstructions that presents with barking cough and inspiratory stridor.

Description

  • The term croup is used to refer to viral laryngotracheitis or LBT. It is a common viral illness presenting with nonspecific upper respiratory symptoms such as coryza, cough, and rhinorrhea.
  • Croup causes upper airway inflammation and obstruction leading to pathognomonic barking cough and inspiratory stridor; symptoms start gradually and are worse at nighttime. Other symptoms are skin rash, conjunctivitis, and lymphadenopathies.

Epidemiology

  • Croup is typically self-limited and it affects approximately 3% of children 6 months to 3 years of age with a peak around the 2nd year of life.
  • The vast majority are considered mild cases; however, croup accounts for 5% of annual hospitalization.
  • Less than 3% require intubation.
  • Predominant sex: male > female (1.5:1)

Incidence
  • Six cases per year per 100 children <6 years old.
  • 15% of emergency department visits for upper respiratory disease in children
  • 1.5–6% of cases require hospitalization.
  • <3% of those require intubation.
  • 60% of barking cough resolved within 48 hours and only 2% have symptoms persisting for longer than five nights.

Etiology and Pathophysiology

  • Subglottic region/larynx is entirely encircled by the cricoid cartilage.
  • Inflammatory edema and subglottic mucus production decrease airway radius.
  • Small children have small airways with more compliant walls.
  • Negative-pressure inspiration pulls airway walls closer together.
  • The anatomically small airway is more susceptible to compromise and narrowing caused by the combined edema, mucus secretions, and increased compliance. Small decrease in airway radius causes significant increase in resistance (Poiseuille law: resistance proportional to 1/radius4).
  • Typically caused by viruses that initially infect oropharyngeal mucosa and then migrate inferiorly
  • Parainfluenza virus is the most common pathogen, responsible for over 75% of cases.
    • Type 1 is the most common, causing 18% of all cases of croup.
    • Type 3 is associated with severe illness.
    • Types 2 and 4 are also common.
  • Other viruses: RSV, paramyxovirus, influenza virus type A or B, adenovirus, rhinovirus, enteroviruses (coxsackie and echo), reovirus, measles virus where vaccination not common, and metapneumovirus
  • Haemophilus influenzae type B now rare with routine immunization
  • Mycoplasma pneumoniae and diphtheria have been reported.
  • Measles has been rarely reported in patients with croup in populations inadequately vaccinated.

Genetics
Noncontributory except in those with acquired immunodeficiencies who are at higher risk

Risk Factors

Prior intubations, prematurity, and age <3 years increase the risks for recurrent croup (more than two episodes per year).

General Prevention

Croup spreads through droplets. Children should be considered contagious up to 3 days after the start of illness and/or until afebrile. There is not a specific vaccine for croup, but seasonal influenza vaccine may contribute to decreased risk.

Commonly Associated Conditions

  • If recurrent (>2 episodes in a year) or during first 90 days of life, consider host factors or allergic factors
  • Underlying anatomic abnormality (e.g., subglottic stenosis)
  • Paradoxical vocal cord dysfunction
  • Gastroesophageal reflux disease
  • Neonatal intubation

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