Which physical findings suggest croup?

Updated: Oct 09, 2019
  • Author: Germaine L Defendi, MD, MS, FAAP; Chief Editor: Russell W Steele, MD  more...
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Inflammation and edema of the subglottic larynx and trachea, especially near the cricoid cartilage, are most clinically significant. Histologically, the involved area is edematous, with cellular infiltration located in the lamina propria, submucosa, and adventitia. The infiltrate contains lymphocytes, histiocytes, neutrophils and plasma cells. Parainfluenza virus activates chloride secretion and inhibits sodium absorption across the tracheal epithelium, contributing to airway edema. The anatomical area impacted is the narrowest part of the pediatric airway; accordingly, swelling can significantly reduce the diameter, limiting airflow. This narrowing results in the seal-like barky cough, turbulent airflow, stridor, and chest wall retractions. Endothelial damage and loss of ciliary function also occur. A mucoid or fibrinous exudate partially occludes the lumen of the trachea. Decreased mobility of the vocal cords due to edema leads to the associated hoarseness.

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