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Overview of Interstitial Lung Disease

(Diffuse Parenchymal Lung Diseases)

By Joyce Lee, MD, MAS, Assistant Professor, Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado Denver

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Interstitial lung diseases are a heterogeneous group of disorders characterized by alveolar septal thickening, fibroblast proliferation, collagen deposition, and, if the process remains unchecked, pulmonary fibrosis. Interstitial lung diseases can be classified using various criteria (eg, acute vs chronic, granulomatous vs nongranulomatous, known cause vs unknown cause, primary lung disease vs secondary to systemic disease).

Among the numerous possible causes are most connective tissue disorders and occupational lung exposures and many drugs (see Table: Causes of Interstitial Lung Disease). A number of interstitial lung diseases of unknown etiology have characteristic histology, clinical features, or presentation and thus are considered unique diseases, including

In up to 30% of patients who have interstitial lung diseases with no clear cause, the disorders are distinguished primarily by characteristic histopathologic features; these disorders are termed the idiopathic interstitial pneumonias.

Causes of Interstitial Lung Disease



Connective tissue disorders

Ankylosing spondylitis (rare)

Behçet syndrome (very rare)

Dermatomyositis and polymyositis

Goodpasture syndrome

IgG-4 related disease

Mixed connective tissue disease


Sjögren syndrome


Systemic sclerosis

Undifferentiated connective tissue disease


Selected list: Amphotericin B, bleomycin, busulfan, carbamazepine, chlorambucil, cocaine, cyclophosphamide, diphenylhydantoin, flecainide, heroin, melphalan, methadone, methotrexate, methylphenidate, methysergide, mineral oil (via chronic microaspiration), nitrofurantoin, nitrosoureas, procarbazine, silicone (sc injection), tocainide, vinca alkaloids (with mitomycin)

Occupational and environmental exposure

Inorganic (selected): Aluminosis (caused by exposure to metallic aluminum powder), asbestosis, baritosis, berylliosis, coal workers’ pneumoconiosis, exposure to hard metals (eg, cadmium, cobalt, titanium oxide, tungsten, vanadium carbides), radiation fibrosis, siderosis, silicosis, stannosis, talc pneumoconiosis

Organic (selected): Bagassosis, bird fancier’s lung, coffee worker’s lung, farmer’s lung, hot tub lung, humidifier lung, malt worker’s lung, maple bark stripper’s lung, mushroom worker’s lung, tea grower’s lung




Parasitic infection

Mycobacterial infection

Viral infection


Eosinophilic granulomatosis with polyangiitis

Giant cell arteritis (rare)

Granulomatosis with polyangiitis

Microscopic polyangiitis

Polyarteritis nodosa (rare)

Takayasu arteritis (rare)

Idiopathic interstitial pneumonias

Acute interstitial pneumonia

Cryptogenic organizing pneumonia

Desquamative interstitial pneumonia

Idiopathic pleuroparenchymal fibroelastosis

Idiopathic pulmonary fibrosis

Lymphocytic interstitial pneumonia

Nonspecific interstitial pneumonia

Respiratory bronchiolitis–associated interstitial lung disease

Miscellaneous disorders


Chronic aspiration

Eosinophilic pneumonia

Gaucher disease (rare)

Lipoid pneumonia




Niemann-Pick disease (rare)

Pulmonary alveolar proteinosis

Pulmonary Langerhans cell histiocytosis (granulomatosis)

Pulmonary lymphoma


Tuberous sclerosis

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