ALLERGIC asthma is the most common immunologic pulmonary disease. However, a variety of other inflammatory and genetic lung diseases have immunopathogenic mechanisms. Cystic fibrosis (CF), granulomatous, and interstitial lung disease are important representatives of these immune-mediated diseases.
Hypersensitivity pneumonitis or extrinsic allergic alveolitis is an immunologic inflammatory reaction involving the bronchioles, alveoli, and lung interstitium. Antigens reach the alveoli by inhalation (eg, organic dusts) or enter the alveolar capillary unit via the bloodstream (eg, drugs).1 These agents (Table 10-1) are usually encountered in work, home, or hobby environments.
The prevalence of hypersensitivity pneumonitis is estimated to be between 7% and 15% of exposed individuals. The most frequent antigens associated with the disease are derived from thermophilic actinomycetes. These organisms thrive best at 60°C in moldy compost and have been isolated from soil, hay, and forced-air heating and cooling systems in which water is stagnant. Farmer's lung,
Fink JN, Kelly KJ. Immunologic Aspects of Granulomatous and Interstitial Lung Diseases and of Cystic Fibrosis. JAMA. 1992;268(20):2874-2881. doi:10.1001/jama.1992.03490200126014