Eosinophilic Pneumonias

The eosinophilic pneumonias are a heterogeneous group of diseases characterized by an increase in eosinophils in lung tissue or bronchoalveolar lavage fluid. Many, but not all, of the eosinophilic pneumonias are also associated with a peripheral blood eosinophilia. The etiologies of eosinophilic lung disease are wide ranging and include parasitic infections, medications or other toxins, autoimmune and inflammatory disease, and malignancies. Some eosinophilic pneumonias have no proven cause or inciting event and are classified as idiopathic. An accurate diagnosis can prove difficult and often relies on a combination of a thorough history and physical examination, including travel and medication history, laboratory and radiographic evaluation, and, in some instances, bronchoscopic and histologic evaluation. Early and accurate diagnosis is imperative in certain diseases, such as acute eosinophilic pneumonia, as delayed diagnosis and treatment can lead to fatal lung disease. Corticosteroids are the mainstay of treatment for many of the eosinophilic pneumonias, particularly for both acute and chronic eosinophilic pneumonias, and prognosis is typically excellent provided treatment is initiated in a timely manner.