Croup is a syndrome in which there is inspiratory stridor, cough and hoarseness, due to varying degrees of laryngeal obstruction . A schematic representation of the pathogeneses of croup is presented in Figure 1. In an individual case, the clinical manifestations of croup may be entirely the result of spasm or edema or any combination of the two. Further, a foreign body or extrinsic mass which encroaches upon the laryngeal airway may be accompanied by varying degrees of spasm and edema. In addition to the larynx, the rhinopharynx and tracheobronchial tree may be simultaneously involved if the basic etiology is infectious.
CLASSIFICATION OF ETIOLOGY
For the purposes of this discussion, the etiology of the croup syndrome will be considered as being due to infectious, mechanical or allergic factors (Table I). Traditionally, most classifications of croup have included in addition another distinct category, i.e., "spasmodic" croup. Typically, this form of croup was described as developing suddenly at night, tending to be recurrent and usually associated with minor upper respiratory infection. This type of disease was said to be due to allergy or immaturity of the larynx and to occur in "the nervous type of child." No doubt a major portion of the laryngeal obstruction in this form of the disease is due to spasm with a lesser degree of actual subglottic edema. However, there is increasing evidence that the laryngeal spasm is apparently triggered by, and associated with, a preceding viral upper respiratory infection in a majority of cases. [SEE TABLE I IN SOURCE PAGE].
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