Chapter 18: Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) occurs in patients with asthma or cystic fibrosis resulting in pulmonary infiltrates, tenacious mucus plugs that harbor hyphae of Aspergillus fumigatus, elevations of total serum IgE concentration and peripheral blood, and sputum eosinophilia. Bronchiectasis is an irreversible complication of ABPA. The key to early diagnosis is considering ABPA in anyone with asthma or cystic fibrosis and a positive skin test to Aspergillus and /or recurrent infiltrates on radiographs. The differential diagnosis for ABPA in patients with asthma includes diseases in which there is an overlap of asthma, peripheral blood eosinophilia, and radiographic infiltrates. Examples include chronic eosinophilic pneumonia, Churg-Strauss syndrome, drug-induced pulmonary infiltrates, infection with a parasite, asthma with atelectasis, and lymphoma. Mucus plugging causing a “tree in bud” pattern on CT examination of the lungs may be from ABPA or other conditions such as nontuberculous (atypical) mycobacteria (Mycobacteria avium‐intracellulare complex). Prednisone is indicated to clear pulmonary infiltrates, and a usual course is for 3 months. Itraconazole and voriconazole are adjunctive and drug‐drug interactions must be considered as azoles decrease elimination of various medications. Although not familial in most patients, presentation of Asp f1 antigen is restricted to specific major histocompatability complex class II molecules, HLA-DR2 and HLA-DR5. There is an increased number of CD4⁺ Th2 lymphocytes in bronchoalveolar lavage, and Aspergillus fumigatus can serve as a growth factor of eosinophils potentiating the effects of IL-3, IL-5, and granulocyte colony-stimulating factor.