Snapshot A 68-year-old man presents to the emergency department for worsening shortness of breath. His dyspnea was most notable with exertion; however, over the course of the past several months, it presented at rest. He reports that he has a non-productive cough and denies have any sinus pain, fever, malaise, chills, or night sweats. He has a past medical history of hypertension and hyperlipidemia. He is a retired aircraft mechanic and has smoked 1 pack of cigarettes daily for the past 45 years. His temperature is 98.6°F (37°C), blood pressure is 134/90 mmHg, pulse is 106/min, respirations are 23/min, and oxygen saturation is 88% on room air. On physical exam, the patient is alert to person but not place or time. There are rales on pulmonary auscultation and digital clubbing. A chest radiograph demonstrates a reticular pattern and honeycombing. Introduction Definition inflammatory lung process that leads to alveolar wall thickening, impairing gas exchange Etiology Environmental coal worker pneumoconiosis silicosis asbestosis associated with roofing work, navy shipyard work associated with pleural plaques on chest imaging may see ferruginous bodies on histology asbestos fibers coated with iron and calcium berylliosis Granulomatous disease sarcoidosis granulomatosis with polyangiitis eosinophillic granulomatosis with polyangiitis histiocytosis x Alveolar filling disease Goodpasture syndrome alveolar proteinosis pulmonary hemosiderosis Hypersensitivity lung disease eosinophilic pneumonitis hypersensitivity pneumonitis Drugs amiodarone bleomycin phenytoin Pathogenesis distal airspace tissue injury (due to a myriad of causes) leads to abnormal wound healing causes structural remodeling, where collagenous fibrosis ensues, impairing gas exchange Presentation Symptoms and physical exam findings differ depending on the underlying cause; for example, patients with pulmonary sarcoidosis may have erythema nodosum Symptoms dyspnea (initially with exertion and as the disease progresses, then at rest) cough fatigue Physical exam rales on pulmonary auscultation digital clubbing cyanosis in advanced disease Imaging Chest radiography indication typically initial imaging option in the workup of interstitial lung disease findings reticular pattern honeycombing High-resolution CT scan of the chest indication diagnostic and helps narrow the cause of interstitial lung disease Studies Pulmonary function tests indication obtained in virtually all patients with interstitial lung disease aids in assessing severity of lung disease and determines whether there is an obstructive, restrictive, or mixed lung patter Differential Heart failure differentiating factors patients may have peripheral edema and hemoptysis Pulmonary embolism differentiating factors patients will have a filling defect on CT angiogram of the chest Treatment Of note, treatment is dependent upon the underlying cause Conservative smoking cessation and influenza and pneumococcal vaccines indication should be given to all patients with interstitial lung disease, unless contraindicated Medical intravenous corticosteroids indication first-line therapy for patients for acute respiratory therapy intravenous cyclophosphamide indication second-line therapy for patients for acute respiratory therapy Complications Irreversible pulmonary fibrosis Respiratory failure Prognosis Variable and depends on the underlying cause