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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 134-1). ILDs are nonmalignant and noninfectious, and they are typically chronic. The differential diagnosis of ILDs often includes infections (e.g., atypical mycobacteria, fungi) and malignancy (e.g., lymphangitic carcinomatosis). One of the most common ILDs associated with a granulomatous reaction, sarcoidosis, is discussed in Chap. 166. 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.
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APPROACH TO THE PATIENT: Interstitial Lung Disease
History: Common presenting symptoms for pts with ILDs include dyspnea and nonproductive cough. Symptom onset and duration can assist in the differential diagnosis. Chronic symptoms (over months to years) are typically seen in most ILDs, including idiopathic pulmonary fibrosis (IPF), pneumoconioses, connective tissue diseases, and pulmonary Langerhans cell histiocytosis (PLCH or eosinophilic granuloma). Subacute symptoms (over weeks to months) can also be observed in many ILDs, especially in sarcoidosis, drug-induced ILDs, cryptogenic organizing pneumonitis (COP, also known as bronchiolitis obliterans with organizing pneumonia [BOOP]), and alveolar hemorrhage syndromes. Acute presentations are uncommon for ILDs but are typically observed with acute interstitial pneumonia (AIP), and they can also occur with eosinophilic pneumonia and hypersensitivity (HS) pneumonitis. Sudden onset of dyspnea can indicate a pneumothorax, which occurs in PLCH and tuberous sclerosis/lymphangioleiomyomatosis. Fatigue and weight loss are common in all ILDs. Episodic presentations also are unusual, but ...