Answer - Allergic Bronchopulmonary Aspergillosis (ABPA)

The PA chest radiograph [Figure - 1] demonstrates thick tubular branching opacities in the left middle and lower zone radiating outwards from the prominent left hilum. The selected CT images reveal tubular branching opacities giving a typical 'finger in glove' appearance. [Figure - 2],[Figure - 3]. This pattern is suggestive of ABPA.

Relevant serology revealed a markedly elevated total serum IgE (3649ng/ml). Aspergillus-specific IgE and IgG in the serum were positive. There was immediate-type cutaneous reactivity to the Aspergillus fumigatus a ntigen. Blood workup revealed eosinophilia (1200 cells/µl).

Discussion

ABPA represents a Type I and Type III (IgE and IgG-mediated) hypersensitivity reaction to the endobronchial growth of the Aspergillus species. ^[1] It is seen predominantly in patients with asthma but also occurs in patients with cystic fibrosis. These two groups of patients account for the majority of ABPA cases. However, ABPA uncommonly occurs in the absence of these conditions. ^[2]

In ABPA there is eosinophilic infiltration and mucus plugging of the airway. The Aspergillus does not invade the bronchial wall or surrounding lung. ^[2]

The disorder is characterized by chest radiographic infiltrates, specific serological status and cutaneous sensitivity to A. fumigatus. ABPA may be subdivided into the following two groups: patients with or without central bronchiectasis. The essential criteria for diagnosis of the group with ABPA and central bronchiectasis are asthma, immediate skin reactivity to Aspergillus antigens, serum IgE level > 1000ng/ml and central bronchiectasis . Patients without central bronchiectasis are labeled ABPA-seropositive and the minimal criteria for diagnosis are asthma, immediate skin reactivity to Aspergillus, serum IgE level > 1000ng/ml, history of pulmonary infiltrates and elevated levels of serum IgE and IgG antibodies to A. fumigatus . A positive sputum culture for A. fumigatus is not essential for diagnosis. ^[3]

There is a range of CT findings in patients with ABPA. Central bronchiectasis is a common finding. The bronchiectasis is usually varicose or cystic in appearance and the frequent formation of mucus plugs containing fungus and inflammatory cells results in a characteristic pattern of mucoid impaction, atelectasis or consolidation. Bronchial wall thickening is frequent and air-fluid levels may be detected in dilated, cystic airways. Ancillary findings include evidence of peripheral airway disease, with mucus impaction in bronchioles resulting in a tree-in-bud pattern or mosaic attenuation because of bronchiolar obstruction with resulting air trapping. High CT attenuation numbers have been measured in the central impacted mucus, presumably representing the presence of calcium or metallic ions within viscous mucus. The prevalence of this finding has been noted to be as high as 28% in one series and when present should be considered characteristic. ^[1] High-resolution CT (HRCT) in asthmatic patients showing bronchiectasis affecting three or more lobes with centrilobular nodules and mucoid impaction, are signs also considered highly suggestive of ABPA. ^[4] Although ABPA has classically been associated with central bronchiectasis, this finding is neither sensitive nor specific for ABPA. ^[5],[6] Other described imaging appearances of ABPA in the literature include pleural thickening/effusions and emphysematous bullae (indication of underlying airway obstruction). ^[2]

The mainstay of treatment is oral corticosteroids, which leads to relief of bronchospasm, clearing of pulmonary infiltrates and a decrease in IgE levels and peripheral eosinophils. ^[3]