REVIEW OF FUNGUS-INDUCED ASTHMATIC REACTIONS

Fungus-induced obstructive airway disease in atopic individuals can be differentiated into two categories: first, uncomplicated asthmatic re actions due to high but transient exposure to fungal spores (fungal as thma), resulting in a T-H2-type response with immunoglobulin E-mediate d reactions and eosinophilic inflammation; and second, a more complex asthmatic reaction due to colonization of the mucus-epithelial surface by virulent protease-producing fungi. The latter condition stimulates as exaggerated immunological response including all subclasses of ant ibodies directed against the microorganism and an intense eosinophilic infiltrate of the airways. The authors propose that the exaggerated i nflammatory response in allergic bronchopulmonary fungosis damages epi thelial cells and underlying tissue cells, resulting in inefficient el imination of the microorganisms and damage to matrix proteins of the l ung tissue by proteases released by both the fungi and degranulating e osinophils. The positive effects of corticosteroids in the treatment o f allergic bronchopulmonary aspergillosis probably results from the da mpening of the inflammatory response and an increase of the efficiency of killing the fungi. Sensitization to fungi is high in childhood and declines rapidly with age, suggesting that younger children may be le ss proficient in clearing fungi from the airways. We propose that insu fficient treatment of fungal asthma may result in damage to the bronch ial mucosa and formation of bronchiectasis.