Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (572 page)

Croup refers to inflammation of the upper airway below the glottis and has been used to describe a variety of upper respiratory conditions in children, including laryngitis, laryngotracheitis, laryngotracheobronchitis, bacterial tracheitis, or spasmodic croup. Croup is usually caused by viral infection, especially parainfluenza virus, but it is occasionally caused by bacteria or an allergic reaction. It typically occurs in children 6 months to 3 years of age, usually during winter and early spring. Epiglottitis may result in acute airway obstruction and should be considered a medical emergency. A stable airway should be assured prior to collection of diagnostic specimens. Bacterial causes of epiglottitis include type b
Haemophilus influenzae
,
S. pneumoniae
, and beta-hemolytic streptococci. The clinical picture in infectious mononucleosis or diphtheria may resemble epiglottitis. TB may cause chronic laryngitis.

   Who Should Be Suspected?

   The hallmark of croup in infants and young children is the barking cough. In older children and adults, hoarseness predominates. Croup is usually a mild and self-limited illness, although significant upper airway obstruction, respiratory distress, and, rarely, death can occur. Symptoms usually begin with nasal irritation, congestion, and coryza. Symptoms generally progress over 12–48 hours to include fever, hoarseness, barking cough, and stridor. Respiratory distress increases as upper airway obstruction becomes more severe. Rapid progression or signs of lower airway involvement suggest a more serious illness.

   Symptoms typically persist for 3–7 days, with a gradual return to normal.

   Usually caused by viruses (80%). Parainfluenza virus (type 1–3) is the most common etiology.

   Diagnostic and Laboratory Findings

Laboratory studies are of limited diagnostic utility but may help guide management in more severe cases.

   CBC: WBC counts can be low, normal, or elevated; WBC counts >10,000 cells/μL are common. CBC differential shows neutrophil or lymphocyte predominance. The presence of a large number of band-form neutrophils is suggestive of primary or secondary bacterial infection.

   Chemistries: Not associated with any specific alterations in serum tests.

   Microbiology: Confirmation of etiologic diagnosis is not necessary, as croup requires only symptomatic therapy. Identification of a specific viral etiology may be necessary to make decisions regarding isolation for patients requiring hospitalization, for initiation of antiviral therapy, or for epidemiologic monitoring purposes.

   Culture: Diagnosis of a specific viral etiology may be made by viral culture of secretions from the nasopharynx or throat.

Suggested Readings

Cherry JD. Croup (Laryngitis, laryngotracheitis, spasmodic croup, laryngotracheobronchitis, bacterial tracheitis, and laryngotracheobronchopneumonitis). In: Feigin RD, Cherry JD, Demmler-Harrison GJ, et al. (eds).
Textbook of Pediatric Infectious Diseases
, 6th ed. Philadelphia, PA: Saunders; 2009.

Rihkanen H, Rönkkö EB, Nieminen T, et al. Respiratory viruses in laryngeal croup of young children.
J Pediatr.
2008;152:661–665.

PERTUSSIS (WHOOPING COUGH)

   Definition

Pertussis, a syndrome characterized by prolonged and severe cough, is usually caused by the bacterium
B. pertussis
; however,
B. parapertussis
,
B. holmesii
, and
B. bronchiseptica
may also cause a pertussis syndrome. Infection is highly communicable, with potential for epidemic spread. Infection is transmitted by the direct respiratory route through exposure to droplets generated by an infected individual. Historically, the association of pertussis as a significant cause of morbidity and mortality in infants and children is well described. Implementation of routine immunization resulted in a significant reduction in the incidence of pertussis. However, since a nadir in the 1970s (0.5 cases/100,000), the incidence of pertussis has been increasing (13.4 cases/100,000 in 2012); outbreaks continue to occur in the United States. This increased incidence is likely due to multiple factors, including waning immunity among vaccines, improved diagnostics, and improved reporting. The incidence of pertussis continues to be highest among infants, followed by older children and adolescents. Spread of infection is limited by vaccination, timely diagnosis and reporting to Public Health officials, antimicrobial therapy and prophylaxis, and measures to prevent further transmission by infected patients.