CROUP

Croup is a clinical syndrome characterized by a seal-like barking cough, hoarseness, inspiratory stridor, and often some degree of respiratory distress. The term croup is usually used to refer to acute laryngotracheobronchitis. Other croup-like syndromes can include spasmodic croup and bacterial tracheitis (Table 30.1). Other potential infectious causes of stridor include supraglottitis (epiglottitis), peritonsillar abscess, retropharyngeal abscess, and rarely, diphtheria, whereas noninfectious etiologies include angioneurotic edema, foreign-body obstruction, hemangioma, trauma, neoplasm, subglottic stenosis, or extrinsic compression. Croup is primarily a disease of children between the ages of 1 to 6 with peak incidence between 6 months and 3 years. The parainfluenza viruses (1, 2, and 3) are the most frequent cause with outbreaks occurring predominantly in the winter months. Other occasional causes include respiratory syncytial virus (RSV), influenza, and adenovirus with rare cases secondary to Mycoplasma, Corynebacterium diphtheriae, and herpes simplex virus (HSV). In adults, the causes are also predominantly viral, including reported cases of influenza, parainfluenza, RSV, HSV, and cytomegalovirus (CMV). In either children or adults, most likely secondary bacterial infections with Haemophilus influenzae type b (Hib), staphylococci, Moraxella catarrhalis, and Streptococcus pneumoniae can be seen.

Croup usually follows a relatively mild upper respiratory infection. Its onset is commonly abrupt and occurs in the late evening and night. Viral infection with associated inflammation of the nasopharynx spreads inferiorly to the respiratory epithelium of the larynx and trachea. The subglottic region in children is normally narrow and surrounded by a firm ring of cartilage. Small swelling of this narrow subglottic area will significantly restrict air flow and produce audible inspiratory stridor, while the impairment of the mobility of the vocal cords will produce hoarseness.