Eosinophilic lung disease

Introduction There are numerous diseases associated with pulmonary eosinophilia. They represent a heterogeneous group of diseases that, except for the presence of eosinophils, sometimes bear little clinical relationship to one another. The most common disease associated with eosinophilia is asthma, and the pathologist’s role in the diagnosis is non-existent, except when there are complications. The most common diffuse disease associated with eosinophilia is chronic eosinophilic pneumonia, which may or may not be associated with asthma. These and other less common diseases are discussed in this chapter. Pulmonary Langerhans’ cell histiocytosis (formerly known as eosinophilic granuloma) and hypersensitivity pneumonitis (extrinsic allergic alveolitis, which is rarely associated with tissue eosinophilia) are discussed in Chapters 34 and 12, respectively. Introduction Asthma is one of the commonest respiratory disorders and is characterized by airway hyperresponsiveness and inflammation. Over the past few decades, the prevalence of asthma has increased and affects as many as 300 million persons worldwide.