USMLE

Parainfluenza Virus (Croup)

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Viruses - RNA Viruses
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Summary

The parainfluenza virus is a paramyxovirus that causes croup. Croup generally presents with a barking seal-like cough. Severe upper airway obstruction in croup can also cause pulsus paradoxus. Finally, patients with croup have a characteristic steeple sign on their x-ray scans, which is indicative of a narrowing in the upper respiratory tract.

Key Points

  • Parainfluenza virus
    • Transmission
      • Respiratory droplets or fomite exposure
    • Presentation
      • Croup (acute laryngotracheobronchitis)
        • barking “seal-like” cough and inspiratory stridor
        • Severe croup can lead to pulsus paradoxus secondary to upper airway obstruction
      • Narrowing of upper trachea and subglottis leads to characteristic steeple sign on X-ray
    • Treatment
      • Supportive care; no antivirals indicated