Allergic bronchopulmonary aspergillosis with atopic, nonatopic, and sans asthma-Factor analysis

Background: Allergic bronchopulmonary aspergillosis (ABPA) develops in the presence or absence of asthma, either atopic or nonatopic. We have tried to explore the essential components in the pathogenesis of the disease, which are either consistent and variable according to the presence and type of asthma. Methods: Non-cystic fibrosis ABPA cases satisfying Asano's criteria were extracted from a prospective registry of ABPA and related diseases in Japan between 2013 and 2023. According to the type of preceding asthma, ABPA was classified into three groups: ABPA sans asthma (no preceding asthma), ABPA with atopic asthma, and ABPA with nonatopic asthma. Exploratory and confirmatory factor analyses were performed to identify the components that determined the clinical characteristics of ABPA. Results: Among 106 cases of ABPA, 25 patients (24%) had ABPA sans asthma, whereas 57 (54%) and 24 (23%) had ABPA with atopic and nonatopic asthma, respectively. Factor analysis identified three components: allergic, eosinophilic, and fungal. Patients with atopic asthma showed the highest scores for the allergic component (p <.001), defined by total and allergen-specific IgE titers and lung opacities, and the lowest scores for the fungal component defined by the presence of specific precipitin/IgG or positive culture for A. fumigatus. Eosinophilic components, including peripheral blood eosinophil counts and presence of mucus plugs/high attenuation mucus in the bronchi, were consistent among the three groups. Conclusion: The eosinophilic component of ABPA is considered as the cardinal feature of ABPA regardless of the presence of preceding asthma or atopic predisposition.