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Snapshot
  • A 4-year-old girl presents to the emergency room for a cold. For the past day, she has had a low-grade fever and has been having increasing difficulty breathing. She has a very loud cough, almost like a seal barking, according to her mother. On physical exam, she has notable inspiratory stridor, accessory muscle use, and a barking cough. She is immediately given a single dose of steroids and given racemic epinephrine with some improvement.
Introduction
  • Classification
    • parainfluenza virus
      • an enveloped, nonsegmented, linear (-) single-stranded RNA virus
        • must have its own RNA-dependent RNA polymerase in order to replicate
      • helical structure
      • a paramyxovirus
    • transmission via respiratory secretions
  • Epidemiology
    • demographics
      • causes croup and bronchiolitis in children
    • location
      • lungs
  • Pathogenesis
    • virus has 3 virulence factors
      • hemagglutinin in the membrane
        • binds sialic acid and aids in viral entry into cells
      • neuraminidase
        • helps propagate viral progeny
      • fusion proteins
        • multi-nucleated giant cells
        • helps mediate virus and cell membrane fusion, ultimately resulting in infection of the host cell
    • primarily infects epithelial cells of the nasopharynx and then travels to the airways
  • Associated conditions
    • most commonly causes croup in children, also known as acute laryngotracheobronchitis
    • bronchiolitis in children < 2 years of age
    • pneumonia
  • Prognosis
    • most cases resolve without complications
Presentation
  • Symptoms
    • “seal-like” barking cough in croup
    • difficulty breathing
  • Physical exam
    • fever
    • inspiratory stridor
    • accessory muscle use
    • pulsus paradoxus with severe croup and upper airway obstruction
Imaging
  • Chest radiography
    • indication
      • all patients
    • findings
      • in croup, may show a steeple sign indicating subglottic narrowing
Studies
  • Making the diagnosis
    • based on clinical presentation
Differential
  • Acute epiglottitis
    • distinguishing factors
      • patients typically have drooling, high fever, and dysphagia
      • a medical emergency
      • absence of barking cough
Treatment
  • Management approach
    • management depends on whether patients have bronchiolitis or croup or pneumonia but centers around supportive care
  • Conservative
    • supportive care
      • indication
        • all patients
      • modalities
        • supplemental oxygen
        • nasal suctioning
        • hydration
  • Medical
    • single dose of steroids
      • indication
        • croup
    • nebulized epinephrine
      • indications
        • croup
Complications
  • Respiratory failure
  • Pneumonia
 

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