Abstract and Introduction
The eosinophilic lung diseases are a group of pulmonary disorders characterized by an increase in blood and/or lung eosinophils. These disorders can be primary pulmonary disorders or the secondary manifestation of other systemic or pulmonary conditions, infection, drug reaction, or malignancy. The approach to a patient with eosinophilic lung disease involves a thorough history and physical examination, review of exposures and appropriate testing, often including bronchoscopy or lung biopsy, to establish a specific etiology and determine therapy. Eosinophilic lung disease can be suspected based on either the finding of pulmonary disease with blood eosinophilia, pulmonary disease with bronchoalveolar lavage eosinophilia, or pulmonary disease with lung tissue eosinophilia on lung biopsy.
The eosinophilic lung diseases are a diverse group of disorders that are accompanied by eosinophilic infiltration of the airways, alveoli, or interstitium of the lung. Some of these disorders exclusively affect the lung, whereas others are part of a systemic process.
Eosinophils have been known to play an important role in the pathogenesis of airways disorders. The presence of an eosinophil inflammatory response in asthma has been well described; however, the presence of an eosinophilic inflammatory response has not always correlated well with symptoms and measures of pulmonary function. More recently, studies have better characterized asthma based on several clinical and molecular phenotypes. This work has shown that in different patients asthma can be an eosinophilic and a noneosinophilic airway process. Some patients have airway eosinophilia without symptoms of wheezing, dyspnea, or airway hyperresponsiveness. These patients with eosinophilic bronchitis present with symptoms of chronic cough.
Eosinophilic lung diseases were first described as PIE syndromes—pulmonary infiltrates with (blood) eosinophilia. More recently, it has been recognized that several lung diseases may have substantial eosinophil infiltration in the lungs but have little or no increase in the peripheral blood eosinophil numbers. These diseases may not be correctly diagnosed unless either bronchoalveolar lavage (BAL) or lung biopsy is performed. The most common eosinophilic lung diseases include simple pulmonary eosinophilia, chronic eosinophilic pneumonia, acute eosinophilic pneumonia, Churg-Strauss syndrome (CSS), idiopathic hypereosinophilic syndrome, allergic bronchopulmonary aspergillosis, bronchocentric granulomatosis, certain parasitic infections, and certain drug reactions.
Patients presenting with an undifferentiated eosinophilic lung disease can present a diagnostic challenge, but by using a combination of clinical history and presentation, radiographic tests, laboratory studies, BAL, and occasionally lung biopsy, patients can usually be grouped into one of the specific diseases discussed in this article ( Table 1 ).
Semin Respir Crit Care Med. 2012;33(5):555-571. © 2012 Thieme Medical Publishers