Interstitial lung disease
|Interstitial lung disease|
|Classification and external resources|
End-stage pulmonary fibrosis of unknown origin, taken from an autopsy in the 1980s.
|ICD-9||518.89, 508.1, 515, 516.3, 714.81, 770.7|
Interstitial lung disease (ILD), also known as diffuse parenchymal lung disease (DPLD), refers to a group of lung diseases affecting the interstitium (the tissue and space around the air sacs of the lungs).  It concerns alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues.
The term ILD is used to distinguish these diseases from obstructive airways diseases.
Prolonged ILD may result in pulmonary fibrosis, but this is not always the case. The term Idiopathic pulmonary fibrosis is used to describe interstitial lung disease for which no obvious cause can be identified (idiopathic), and is associated with typical radiographic (basal and pleural based fibrosis with honeycombing) and pathologic (temporally and spatially heterogeneous fibrosis, histopathologic honeycombing and fibroblastic foci) findings.
ILD may be classified according to the cause. One method of classification is as follows: (Mnemonic- Inhaled Drugs Can Infect Idiopathic Malignancy)
- Inhaled substances
- Drug induced
- Connective tissue disease
- Infection (mnemonic- TB is CRAP)
- Lymphangitic carcinomatosis
Investigation is tailored towards the symptoms and signs. A proper and detailed history looking for the occupational exposures, and for signs of conditions listed above is the first and probably the most important part of the workup in patients with interstitial lung disease. Pulmonary function tests usually show a restrictive defect with decreased diffusion capacity (DLCO) .
A lung biopsy is required if the clinical history and imaging are not clearly suggestive of a specific diagnosis or malignancy cannot otherwise be ruled out. In cases where a lung biopsy is indicated, a trans-bronchial biopsy is usually unhelpful, and a surgical lung lung biopsy is often required.
Role of radiology in the diagnosis of interstitial lung disease
High resolution CT of the chest is the preferred modality, and differs from routine CT of the chest. Conventional (regular) CT chest examines 7–10 mm slices obtained at 10 mm intervals; high resolution CT examines 1-1.5 mm slices at 10 mm intervals using a high spatial frequency reconstruction algorithm. The HRCT therefore provides approximately 10 times more resolution than the conventional CT chest, allowing the HRCT to elicit details that cannot otherwise be visualized.
Radiologic appearance alone however is not adequate and should be interpreted in the clinical context, keeping in mind the temporal profile of the disease process.
Interstitial lung diseases can be classified according to radiologic patterns
Acute: Alveolar hemorrhage syndromes, acute eosinophilic pneumonia, acute interstitial pneumonia, cryptogenic organizing pneumonia
Chronic: Chronic eosinophilic pneumonia, cryptogenic organizing pneumonia, lymphoproliferative disorders, pulmonary alveolar proteinosis, sarcoidosis
Linear or reticular opacities
Acute: Pulmonary edema
Chronic: Idiopathic pulmonary fibrosis, connective tissue associated interstitial lung diseases, asbestosis, sarcoidosis, hypersensitivity pneumonitis, drug induced lung disease
Acute: Hypersensitivity pneumonitis
Chronic: Hypersensitivity pneumonitis, sarcoidosis, silicosis, coal workers pneumoconiosis, respiratory bronchiolitis, alveolar microlithiasis
Chronic: Pulmonary langerhans cell histiocytosis, pulmonary lymphangioleiomyomatosis, honeycomb lung caused by IPF or other diseases
Ground glass opacities
Acute: Alveolar hemorrhage syndromes, pulmonary edema, hypersensitivity pneumonitis, acute inhalational exposures, drug induced lung diseases, acute interstitial pneumonia
Chronic: Nonspecific interstitial pneumonia, respiratory bronchiolitis associated interstitial lung disease, desquamative interstitial pneumonia, drug induced lung diseases, pulmonary alveolar proteinosis
Thickened alveolar septa
Acute: Pulmonary edema
Chronic: Lymphangitic carcinomatosis, pulmonary alveolar proteinosis, sarcoidosis, pulmonary veno occlusive disease
Upper lung predominance
Pulmonary Langerhans cell histiocytosis, silicosis, coal workers pneumoconiosis, carmustine related pulmonary fibrosis
Lower lung predominance
Idiopathic pulmonary fibrosis, pulmonary fibrosis associated with connective tissue diseases, asbestosis, chronic aspiration
Central predominance (perihilar)
Idiopathic pulmonary fibrosis, chronic eosinophilic pneumonia, cryptogenic organizing pneumonia
Pleural effusion or thickening
Pulmonary edema, connective tissue diseases, asbestosis, lymphangitic carcinomatosis, lymphoma, lymphangioleiomyomatosis, drug induced lung diseases
Sarcoidosis, silicosis, berylliosis, lymphangitic carcinomatosis, lymphoma, lymphocytic interstitial pneumonia
ILD is not a single disease, but encompasses many different pathological processes. Hence treatment is different for each disease.
If a specific occupational exposure cause is found, the person should avoid that environment. If a drug cause is suspected, that drug should be discontinued.
Many idiopathic and connective tissue-based causes of ILD are treated with corticosteroids, such as prednisolone. Some patients respond to immunosuppressant treatment. Patients with hypoxemia may be given supplemental oxygen.
- King TE (August 2005). "Clinical advances in the diagnosis and therapy of the interstitial lung diseases". Am. J. Respir. Crit. Care Med. 172 (3): 268–79. doi:10.1164/rccm.200503-483OE. PMID 15879420.
- "Frequently Asked Questions About Interstitial Lung Disease - University of Chicago Medical Center".
- Bourke SJ (August 2006). "Interstitial lung disease: progress and problems". Postgrad Med J 82 (970): 494–9. doi:10.1136/pgmj.2006.046417. PMC 2585700. PMID 16891438.
- Ryu, JH; Olson, EJ; Midthun, DE; Swensen, SJ (Nov 2002). "Diagnostic approach to the patient with diffuse lung disease.". Mayo Clinic proceedings 77 (11): 1221–7; quiz 1227. PMID 12440558.
- "Interstitial Lung Disease/Pulmonary Fibrosis Northwestern Chicago Frequently Asked Questions".
- "Interstitial lung disease: Treatments and drugs - MayoClinic.com".
- Kotloff, RM; Thabut, G (Jul 15, 2011). "Lung transplantation.". American journal of respiratory and critical care medicine 184 (2): 159–71. PMID 21471083.
- Whelan, TP (Mar 2012). "Lung transplantation for interstitial lung disease.". Clinics in chest medicine 33 (1): 179–89. PMID 22365254.
For more information and resources on ILD, please visit the links below:
- AIMIP Onlus - Italian Interstitial Lung Diseases No-Profit Organization
- 00736 at CHORUS
- 1476788304 at GPnotebook
- Pulmonary Fibrosis at the US National Library of Medicine Medical Subject Headings (MeSH)
- MedlinePlus Overview pulmonaryfibrosis
- coalitionforpf.org - Coalition for Pulmonary Fibrosis: Pulmonary Fibrosis Patient Services, Education; Funding Research to Find a Cure for PF
- GeneReview/NCBI/NIH/UW entry on Pulmonary Fibrosis, Familial
- UCSF Interstitial Lung Disease Program at University of California San Francisco
- Interstitial Lung Disease Program at University of Chicago Medical Center
- Interstitial Lung Disease Center at University of Cincinnati
- Interstitial Lung Diseases Program at Northwestern Medicine in Chicago
- PA-IPF - The Pennsylvania Idiopathic Pulmonary Fibrosis State Registry at University of Pittsburgh
- WASOG - World Association for Sarcoidosis and Other Granulomatous Disorders