Description

• Acute, life-threatening upper airway obstruction due to infraglottic bacterial infection following a primary viral infection (typically parainfluenza or influenza)
• Historically high mortality rates of up to 20% in children (1); more recent experience suggests changing epidemiology resulting in a more atypical presentation and variable course (2) but which can still result in severe, acute, upper airway obstruction
• Affects two major groups of patients in the pediatric age range (1)
  • Those with a native intact airway
  • Those with an artificial airway
• Often preceded by viral infection, such as influenza, parainfluenza, or respiratory syncytial virus (1)
• Staphylococcus is the most common bacteria identified (2).
• Diagnostic hallmarks on endoscopy: ulceration, pseudomembranes in the trachea with thick mucopurulent exudates and mucosal sloughing (1),(2)
• System(s) affected: pulmonary
• Synonym(s): laryngotracheobronchitis; bacterial croup; pseudomembranous croup

Epidemiology

• Incidence: 4 to 8 per 1 million children (1)
• Approximately 0.1/100,000 children-years in United Kingdom
• Peak incidence in children: fall and winter (1)
• Mean age: 5 years (1),(3)
• Infections in adolescents and adults have been reported.

• Rare illness
• Methicillin-resistant Staphylococcus aureus (MRSA) may contribute to changing epidemiology and virulence.

Etiology and Pathophysiology

• Methicillin-sensitive S. aureus (MSSA) accounted for 50% cases in Casazza series (2019) (2).
• Mixed respiratory
• Streptococcus pneumoniae
• In children with artificial airway, most common organisms are S. aureus, Haemophilus influenzae, S. pneumoniae, Pseudomonas aeruginosa, and other gram-negative organisms (1).
• Viral-induced injury to the respiratory epithelium in conjunction with localized immune impairment can predispose individuals to bacterial superinfection.

Genetics
No known genetic predisposition

Risk Factors

• Periods of increased seasonal activity of respiratory viruses
• Reports following tonsillectomy, adenoidectomy, with chronic tracheal aspiration, and with evidence of other concurrent infections, including sinusitis, otitis, pneumonia, or pharyngitis

General Prevention

• Standard precautions, with scrupulous attention to hand washing
• Vaccination against viruses that may predispose to bacterial tracheitis
• In children with artificial airways, periodic surveillance of tracheal cultures can be helpful.

Commonly Associated Conditions

• Consider anatomic abnormalities, foreign bodies as well as recent pharyngeal or laryngeal surgery.
• Predisposing: Down syndrome, immunodeficiency, subglottic hemangioma, tracheoesophageal fistula repair, tracheobronchomalacia
• More common in children with tracheostomy
• Viral coinfection may occur.