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Overview of Interstitial Lung Disease

(Diffuse Parenchymal Lung Diseases)


Joyce Lee

, MD, MAS, University of Colorado Denver

Last full review/revision Sep 2019| Content last modified Sep 2019
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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, history of smoking vs no smoking history).

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

Behçet disease (very rare)

IgG-4 related disease

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)

Genetic disorders

Fabry disease (rare)

Familial pulmonary fibrosis

Hermansky-Pudlak Syndrome

Pulmonary alveolar microlithiasis

Idiopathic interstitial pneumonias


Parasitic infection

Mycobacterial infection

Viral infection

Occupational and environmental exposure

Inorganic (selected): Aluminosis (caused by exposure to metallic aluminum powder), asbestosis, baritosis, beryllium disease, 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 (see Hypersensitivity Pneumonitis)


Miscellaneous disorders

Chronic aspiration

Lipoid pneumonia

Pulmonary lymphoma

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