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Interstitial Lung Disease

The information on these webpages is intended as an educational resource for health professionals, including those working in primary care and respiratory specialists. The information has been developed by health professionals from the Centre of Research Excellence in Pulmonary Fibrosis. It is a general guide and does not replace specialist knowledge or individualised patient care.

Interstitial Lung Diseases (ILDs) are a complex group of more than 200 diseases characterised by some degree of fibrosis and/or inflammation of the lung interstitium. This may result in physiological impairment, causing significant morbidity and mortality. There is a wide spectrum of ILD, and heterogeneity of disease course, with some patients having stable disease, and others progressing very quickly to respiratory failure and death.

While individual ILDs may be considered rare, as a group, prevalence is estimated at around 70-100 per 100,000, and this is increasing year by year.

Interstitial Lung Diseases (ILD) or Pulmonary Fibrosis (PF)?

ILD is the clinically appropriate term for this group of diseases. Pulmonary fibrosis (PF) is a commonly used umbrella term for the large proportion of ILD’s which are characterised by fibrosis or scarring in the lung parenchyma. Note that we use the term PF in all resources and content developed for patients as the better lay term and more commonly understood name for the group of conditions.

Types of ILD

ILD may be idiopathic (otherwise known as the group of idiopathic interstitial pneumonias), or associated with exposure to drugs or environmental triggers, or underlying connective tissue disease. Types and classification of ILDs are summarised in the table below. More is now known about genetic causes of ILD. While this is rare, ILD may be familial, and can be associated with short telomere syndromes which also can have other clinical manifestations. Referral to an ILD specialist centre with genetic testing is advisable in younger patients or patients with a family history of ILD or extrapulmonary features of telomeropathies.

Table: Types and classification of the most common Interstitial Lung Diseases (ILDs)
Interstitial Lung Diseases (ILDs)
ILDs of known association Granulomatous ILDs Idiopathic interstitial pneumonias (IIPs) Miscellaneous ILDs
  • Connective tissue disease
  • Drugs (e.g. nitrofurantoin)
  • Occupational exposures
  • Sarcoidosis
  • Hypersensitivity pneumonitis
Major IIPs

  • Idiopathic pulmonary fibrosis (IPF)
  • Non-specific interstitial pneumonia
  • Cryptogenic organising pneumonia
  • Respiratory bronchiolitis ILD
  • Desquamative interstitial pneumonia
  • Acute interstitial pneumonia
  • Lymphangioleiomyomatosis (LAM)
  • Pulmonary Langerhans cell histiocytosis (histiocytosis X)
Rare IIPs

  • Lymphocytic interstitial pneumonia
  • Idiopathic pleuro-parenchymal fibroelastosis


  • Reference list

    Jo*, H. E., et al. (2018). “Diagnosis and management of idiopathic pulmonary fibrosis: Thoracic Society of Australia and New Zealand and Lung Foundation Australia position statements summary.” Medical Journal of Australia 208(2): 82-88.

    Kolb, M. and M. Vašáková (2019). “The natural history of progressive fibrosing interstitial lung diseases.” Respir Res 20(1): 57.

    Lederer, D. J. and F. J. Martinez (2018). “Idiopathic Pulmonary Fibrosis.” N Engl J Med 378(19): 1811-1823.

    Lynch, D. A., et al. (2018). “Diagnostic criteria for idiopathic pulmonary fibrosis: a Fleischner Society White Paper.” Lancet Respir Med 6(2): 138-153.

    Prasad, J. D., et al. (2017). “The interstitial lung disease multidisciplinary meeting: A position statement from the Thoracic Society of Australia and New Zealand and the Lung Foundation Australia.” Respirology 22(7): 1459-1472.

    Raghu, G., et al. (2018). “Diagnosis of Idiopathic Pulmonary Fibrosis. An Official ATS/ERS/JRS/ALAT Clinical Practice Guideline.” Am J Respir Crit Care Med 198(5): e44-e68.

    Troy, L. and T. J. Corte (2015). “Interstitial lung disease in 2015: where are we now?” Australian Journal for General Practitioners 44(8): 546-552.

    Wells, A. U., et al. (2018). “What’s in a name? That which we call IPF, by any other name would act the same.” Eur Respir J 51(5).

Content and expert review for these Interstitial Lung Disease webpages was contributed by: Prof Tamera Corte, A/Prof Nicole Goh, Prof Anne Holland, A/Prof Yet Khor, Dr Robert Sheehy, Ms Karen Symons and Dr Alan Teoh.