Review Question - QID 100810

The patient's presentation is consistent with extrinsic (allergic) asthma. Occasional eosinophils are observed in the sputum of patients with this condition.

Asthma can be divided into intrinsic and extrinsic types. In intrinsic asthma, infection, exertion, stress, or a drug reaction is responsible for bronchoconstriction. This type of asthma is not allergen-mediated. In extrinsic asthma, an inhaled allergen triggers a type I (IgE-mediated) hypersensitivity reaction that leads to activation of mast cells and eosinophils. The release of inflammatory substances from those cells is then responsible for the bronchoconstriction observed. Approximately 1/3 of asthma cases are allergen-triggered.

Pollart et al. discuss the management of asthma exacerbation and emphasize the goals of correcting severe hypoxemia, reversing airflow obstruction with bronchodilators and decreasing the risk for relapse of symptoms. The combination of multiple doses of inhaled beta-2 agonists and anticholinergics improve lung function in school-age children and decrease hospitalization for severe exacerbations.

Wegmann discusses the molecular biology mediating the eosinophil response in asthma. He notes that there are now novel drugs in development to treat asthma by targeting eosinophils from a variety of angles, including recruitment, activation, chemotaxis, survival and apoptosis.

Illustration A provides a chart comparing the typical characteristics of intrinsic and extrinsic asthma, although exceptions commonly occur.

Incorrect answers:
Answer 1: Patients with allergic asthma typically have a normal chest radiograph (xray).
Answer 2: Patients with asthma have a reduced FEV1.
Answer 4: Asthma is an obstructive lung disease and is, therefore, characterized by a reduced FEV1/FVC ratio.
Answer 5: Ground glass opacities on chest CT are seen in some interstitial lung diseases. This patient's presentation is more consistent with extrinsic allergic asthma.