Chapter 136: Interstitial Lung Disease

Interstitial lung diseases (ILDs) are a group of >200 disease entities characterized by diffuse lung parenchymal abnormalities. ILDs can be classified into two major groups: (1) diseases associated with predominant inflammation and fibrosis, and (2) diseases with predominantly granulomatous reaction in interstitial or vascular areas (Table 136-1). ILDs are nonmalignant and noninfectious, and they are typically chronic. The differential diagnosis of ILDs often includes infections (e.g., atypical mycobacteria, fungi), congestive heart failure, and malignancy (e.g., bronchoalveolar cell carcinoma). One of the most common ILDs associated with a granulomatous reaction, sarcoidosis, is discussed in Chap. 169: Sarcoidosis. Other common ILDs include idiopathic pulmonary fibrosis (IPF) and ILDs related to connective tissue diseases. Many ILDs are of unknown etiology; however, some ILDs are known to be associated with specific environmental exposures including asbestos, radiation therapy, and organic dusts.

TABLE 136-1: Major Categories of Alveolar and Interstitial Inflammatory Lung Disease
Lung response: Alveolitis, interstitial inflammation, and fibrosis
Known Cause
Asbestos	Radiation
	Aspiration pneumonia
Drugs (e.g., nitrofurantoin, amiodarone, methotrexate, rituximab) and chemotherapy drugs	Residual of adult respiratory distress syndrome
Smoking-related Desquamative interstitial pneumonia Respiratory bronchiolitis-associated interstitial lung disease Langerhans cell granulomatosis (eosinophilic granulomatosis of the lung)
Unknown Cause
Idiopathic interstitial pneumonias	Pulmonary alveolar proteinosis
Idiopathic pulmonary fibrosis (usual interstitial pneumonia)	Lymphocytic infiltrative disorders (lymphocytic interstitial pneumonitis associated with connective tissue disease)
	Eosinophilic pneumonias
Acute interstitial pneumonia (diffuse alveolar damage)	Lymphangioleiomyomatosis Amyloidosis
Cryptogenic organizing pneumonia (bronchiolitis obliterans with organizing pneumonia) Nonspecific interstitial pneumonia	Inherited diseases Tuberous sclerosis, neurofibromatosis, Niemann-Pick disease, Gaucher disease, Hermansky-Pudlak syndrome
Connective tissue diseases Systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis, Sjögren syndrome, polymyositis-dermatomyositis	Gastrointestinal or liver diseases (Crohn disease, primary biliary cirrhosis, chronic active hepatitis, ulcerative colitis) Graft-versus-host disease (bone marrow transplantation; solid organ transplantation)
Pulmonary hemorrhage syndromes Goodpasture syndrome, idiopathic pulmonary hemosiderosis, isolated pulmonary capillaritis
Lung response: Granulomatous
Known Cause
Hypersensitivity pneumonitis (organic dusts)	Inorganic dusts: beryllium, silica
Unknown Cause
Sarcoidosis	Bronchocentric granulomatosis
Granulomatous vasculitides	Lymphomatoid granulomatosis
Granulomatosis with polyangiitis (Wegener’s), allergic granulomatosis of Churg-Strauss

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