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The idiopathic interstitial pneumonias (IIPs) encompass a subcategory of interstitial lung diseases (ILDs) that pose significant diagnostic and management challenges. The general diagnostic approach to these disorders is discussed elsewhere in this textbook (Chapter 52), as is the diagnosis and management of idiopathic pulmonary fibrosis (IPF) (Chapter 54). This chapter details the classification, diagnosis, and management of non-IPF forms of IIPs.

In a 2013 update, the American Thoracic Society and European Respiratory Society delineated three categories of idiopathic interstitial pneumonias: the major idiopathic interstitial pneumonias, rare idiopathic interstitial pneumonias, and a separate category for unclassifiable interstitial pneumonias. The major idiopathic interstitial pneumonias include chronic fibrosing interstitial pneumonias (idiopathic pulmonary fibrosis, idiopathic nonspecific interstitial pneumonia), smoking-related interstitial pneumonias (respiratory bronchiolitis–interstitial lung disease, desquamative interstitial pneumonia), and acute/subacute interstitial pneumonias (cryptogenic organizing pneumonia and acute interstitial pneumonia). Rare idiopathic IPs include idiopathic lymphocytic interstitial pneumonia and the newly recognized entity of idiopathic pleuroparenchymal fibroelastosis. The guidelines further demarcated a diagnostic category for unclassifiable IIP, acknowledging the clinical reality that a subset of patients may not fully meet criteria for a specific diagnosis.1 In this chapter, after a description of the specific entities, each section ends with a discussion of current therapeutic options. This information is summarized in Table 55-1.

TABLE 55-1Key Features of Major and Rare Idiopathic Interstitial Pneumonias

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