ETIOLOGY
Reactive airway disease has many causes of which asthma, defined by atopy and entwined with allergic rhinitis and eczema, is the most common.3 A history of prematurity favors lung injury (bronchopulmonary dysplasia), and association with eating or ingestion favors aspiration or a foreign body. Infection with a virus (eg, RSV) or bacteria (eg, Mycobacterium tuberculosis, pneumococcus) can produce transient wheezing; in this setting, patient age determines whether pneumonitis presents as bronchiolitis or cough.
Congenital anomalies of the trachea or pulmonary tree must be suspected in children with birth defect patterns, and wheezing caused by dysphagia and aspiration should be suspected in those with global delays. Singlegene disorders, such as cystic fibrosis, often have associated symptoms and familial cases that reveal the diagnosis. Similarly, a family history of atopy supports the diagnosis of asthma and draws attention to the “allergic march” of eczema/allergic rhinitis/asthma that can be slowed by effective therapy.
Closely intertwined with asthma is bronchiolitis— the most common lower respiratory tract disease in young children. In children younger than 2 years, bronchiolitis is defined by rhinorrhea, cough, wheezing, tachypnea, and increased respiratory effort (grunting, nasal flaring, intercostal/subcostal retractions).4,5 RSV infection is a major contributor to these reactive airway diseases, infecting 90% of children younger than 2 years, with 40% of infections involving the lower respiratory tract. RSV infection causes 90,000 hospitalizations per year in the United States and reinfections can occur throughout life.
Symptoms of bronchiolitis with a negative result on a rapid test for RSV—as in Case 1—identifies a child at risk for recurrent respiratory disease. A diagnosis of bronchiolitis rather than asthma is important because bronchodilator therapies are not recommended for bronchiolitis unless a positive response to this therapy has been previously documented for the patient by objective measures (eg, oxygen saturation, flow parameters).4-6
Evidence of recurrence and findings associated with asthma (atopy by skin testing, positive family history) are needed to determine whether an episode of bronchiolitis foretells a diagnosis of asthma.
DIAGNOSIS
Accurate diagnosis is important to differentiate asthma from disorders that may not respond well to asthma therapy. The latter include allergic rhinitis, gastroesophageal reflux disease, cardiac failure, laryngotracheomalacia, and vocal cord dysfunction.1
A retrospective review of 50 children younger than 3 years evaluated for recurrent respiratory symptoms showed that 20% had wheezing, 12% had wheezing and cough, 11% had cough alone, and 7% had other symptoms (such as, “hard-breathing,” rhinorrhea, or retractions).3 Asthma was diagnosed in 35 of the 50 children, sinusitis in 5, aspiration in 2, and recurrent croup in 1; 7 had no definitive diagnosis at the time of chart review. Those with a diagnosis of asthma were more likely to have recurrent otitis (23 patients), worsening symptoms after exercise (21), a family history of asthma (14), and/or a mother who smoked (10); the patients with asthma were also more likely to snore (11) or have coexisting eczema (7).
The 50 children underwent 1 or more of the following: chest radiography, sweat chloride test, allergy skin test, sinus radiography, and pulmonary function testing/ bronchoscopy.3 Initial chest radiographs often revealed infiltrates during acute attacks; however, findings from subsequent films were normal (with some peribronchial cuffing or perihilar densities), except in children with chronic aspiration. None of the 50 children had pulmonary anomalies, although vascular rings and cystic adenoid malformations have been reported in patients with recurrent respiratory symptoms. In another study, chest radiographs documented asthma findings (hyperinflation with increased lucency, flattened diaphragms, horizontal ribs, increased anteroposterior diameter of the chest) in 94% of 371 patients who had first asthma attacks; 20 of these patients (6%) also had segmental atelectasis and/or pneumonia.6
