Allergic fungal diseases of the lung: pathology.

Allergic responses to molds in the respiratory tract include allergic bronchopulmonary mycoses (ABPM), allergic fungal sinusitis, and allergic reactions to mold spores similar to reactions to dust and other airborne allergens in asthma. In this chapter, we describe the immunopathogenesis, clinical, and pathological features of ABPM that affects 1-2% of subjects with persistent asthma and about 7% of people with Cystic Fibrosis. The inflammatory reaction is triggered by colonization of the bronchial tree with Aspergillus and mediated by IgE, IgG, eosinophil-derived pro-inflammatory proteins, IFN-gamma, and Th2 cytokines. Pathological findings include mucoid impaction, eosinophilic infiltrates, bronchiolitis obliterans, bronchocentric granulomatosis, and even pulmonary fibrosis. Predominant cell types seen include histiocytes, plasma cells, lymphocytes and eosinophils, and fungal hyphae are often detected. A related form of chronic, allergic, inflammatory process can affect the sinuses. The importance of mold allergy as a cause of asthma itself is controversial and generally difficult to establish with certainty, although like dust and pollens, it is clear that molds, including Aspergillus, can induce asthma in susceptible individuals.