Viral Croup: A Current Perspective

Alexander K.C. Leung, MBBS, FRCPC, FRCP (UK & Irel), FRCPCH; James D. Kellner, MD, FRCPC; David W. Johnson, MD, FRCPC


J Pediatr Health Care. 2004;18(6) 

In This Article

Differential Diagnosis

The differential diagnosis of viral croup is listed in the Box(see link in the Table of Contents). Spasmodic croup usually is not preceded by an upper respiratory tract infection, and there is no associated fever (Leung & Cho, 1999). It often occurs with a sudden onset at night and usually resolves in the morning. Spasmodic croup is recurrent in approximately 5% of children, and there may be a family history of atopy (Van Bever et al., 1999).

Epiglottitis tends to occur in older children (2 to 7 years of age). The disease is characterized by an abrupt onset of high fever, toxicity, stridor, dysphagia, and drooling. The child may prefer to sit leaning forward with the mouth open and the tongue somewhat protruding. There is no barky cough. Epiglottitis is rarely seen nowadays because of the widespread use of Haemophilus influenzae type b vaccine (Leung & Jadavji, 1988).

Bacterial tracheitis is usually a superinfection following viral croup but can manifest as a primary infection (Ewig, 2002). The condition can be distinguished from viral croup by the presence of high fever, toxicity, and increasing respiratory distress unresponsive to the conventional treatment for viral croup.

Foreign body aspiration may cause acute stridor. A history of recent aspiration or choking on a foreign body can be obtained in 90% of cases (Leung & Cho, 1999). The most common symptoms of laryngotracheal foreign bodies are cough, stridor, and dyspnea, whereas those of bronchial foreign bodies are cough, decreased breath sounds, wheezing, and dysphagia (Leung & Cho).

In vocal cord paralysis, the stridor typically is biphasic. In unilateral vocal cord paralysis, the infant's cry is weak and feeble; however, usually there is no respiratory distress. In bilateral vocal cord paralysis, the voice is usually of good quality, but there is marked respiratory distress (Leung & Cho, 1999).

Angioneurotic edema may result in acute swelling of the upper airway with resultant stridor and dyspnea. Swelling of the face, tongue, or pharynx also may be present.

Rarely, hypocalcemia may cause laryngospasm (hypocalcemic tetany) and stridor. Other features include irritability, tremors, twitchings, and carpopedal spasm.

Stridor may be a manifestation of a conversion disorder. Characteristically, the onset of psychogenic stridor is sudden but without the expected amount of distress (Leung & Cho, 1999). The neck often is held in a flexed position rather than in an extended position.

The diagnosis of viral croup is mainly a clinical one based on the history and physical findings. Diagnostic studies usually are not necessary. Radiographs of the neck should be considered when aspirated foreign body is suspected, when the diagnosis is in doubt, and when the response to standard treatment is unsatisfactory (Folland, 1997). A "pencil tip" or "steeple sign" of subglottic edema in the anteroposterior view and an overdistended hypopharynx on the lateral view are classical findings in croup (Knutson & Aring, 2004).


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