Allergic bronchopulmonary aspergillosis (ABPA) is an idiopathic inflammatory disease of the lung, characterized by an allergic inflammatory response to colonization of the airways by Aspergillus fumigatus or other fungi. The entity was first described in 1952 by Hinson et al., and then again in 1967, when Scadding recognized an association between the disease and proximal bronchiectasis in areas previously affected by infiltrates (predominantly in the upper lobes).1,2 The first adult case of ABPA was reported in the United States in 1968.3 Although most cases entail hypersensitivity to Aspergillus spp. (i.e., A. fumigatus or niger), the finding of a virtually identical clinical syndrome associated with immune sensitivity to Candida albicans (most commonly), Helminthosporium, Alternaria, Curvularia lunata, Drechslera hawaiiensis, Stemphylium languinosum, Saccharomyces cerevisiae, or Pseudallescheria boydii has led some to use the term allergic bronchopulmonary mycosis to describe the syndrome.4 However, since the predominant causative organism is A. fumigatus (and the commercially available laboratory testing is for this organism and A. niger), ABPA is primarily designated as the diagnosis. In addition, a recently recognized entity appears to be on the continuum between fungal allergy, at one end, and ABPA at the other: severe asthma with fungal sensitivity (SAFS).5
The precise prevalence of ABPA is unknown, in part due to variability in diagnostic criteria used in various studies, the lack of distinction between ABPA and mold-sensitive asthma, and delays in the diagnosis of patients with long-standing disease; however, it is clear that ABPA is a relatively common entity. Estimates are that true ABPA complicates approximately 7% to 14% of cases of chronic steroid-dependent asthma and approximately 7% to 15% of cases of cystic fibrosis (CF). Therefore, it is commonly encountered by pulmonologists and allergists.6,7
Most cases of ABPA are recognized in the third to fifth decade of life, but the disease can also present during childhood. In some patients, it is likely that ABPA starts early in life and continues, unrecognized, until adulthood. Interestingly, familial cases have been reported, suggesting that genetic factors may underlie the development of ABPA.8,9 The spectrum of disease is broad, which can complicate the diagnosis and initiation of corticosteroid-sparing therapy. Patients may be asymptomatic, have mild to moderate asthma, or have severe and debilitating disease that leads to severe bronchiectasis, mucoid Pseudomonas colonization, and the need for lung transplantation. However, if recognized early and managed aggressively, ABPA is treatable, it may enter into remission, and progressive lung damage can be avoided.
For the purposes of this discussion, the focus will be on ABPA. However, clinicians should be cognizant that diagnostic testing for other fungi should be pursued when organisms other than Aspergillus spp. are suspected. In addition, in patients that don’t quite meet criteria of ABPA, a diagnosis of SAFS should be considered as it will affect clinical management.