Eosinophilic Lung Diseases: a Clinical, Radiologic, and Pathologic Overview

Eosinophilic lung diseases are a diverse group of pulmonary disorders associated with peripheral or tissue eosinophilia. They are classified as eosinophilic lung diseases of unknown cause (simple pulmonary eosinophilia [SPE], acute eosinophilic pneumonia [AEP], chronic eosinophilic pneumonia [CEP], idiopathic hypereosinophilic syndrome [IHS]), eosinophilic lung diseases of known cause (allergic bronchopulmonary aspergillosis [ABPA], bronchocentric granulomatosis [BG], parasitic infections, drug reactions), and eosinophilic vasculitis (allergic angiitis, granulomatosis [Churg-Strauss syndrome]). The percentages of eosinophils in peripheral blood and bronchoalveolar lavage fluid are essential parts of the evaluation. Chest computed tomography (CT) demonstrates a more characteristic pattern and distribution of parenchymal opacities than does conventional chest radiography. At CT, SPE and IHS are characterized by single or multiple nodules with a surrounding ground-glass-opacity halo, AEP mimics radiologically hydrostatic pulmonary edema, and CEP is characterized by nonsegmental airspace consolidations with peripheral predominance. ABPA manifests with bilateral central bronchiectasis with or without mucoid impaction. The CT manifestations of BG are nonspecific and consist of a focal mass or lobar consolidation with atelectasis. The most common CT findings in Churg-Strauss syndrome include sub-pleural consolidation with lobular distribution, centrilobular nodules, bronchial wall thickening, and interlobular septal thickening. The integration of clinical, radiologic, and pathologic findings facilitates the initial and differential diagnoses of various eosinophilic lung diseases.