Idiopathic interstitial pneumonias (IIPs) are diffuse interstitial lung diseases of unknown cause. They are characterized by infiltration of the interstitial compartment with inflammatory cells. A useful mnemonic for the American Thoracic Society-European Respiratory classification of IIPs is:
- All Idiopathic Chronic Lung Disease aRe Nonspecific
The mnemonic reflects the frustration of trying to differentiate them on plain film. Indeed, diagnosis depends on HRCT findings, as well as clinical presentation. Even then, some cases require lung biopsy for definitive diagnosis.
- A - acute interstitial pneumonia (AIP). The only acute process in the list.
- I - idiopathic pulmonary fibrosis / usual interstitial pneumonia (IPF / UIP)
- C - cryptogenic organizing pneumonia (COP)
- L - lymphoid interstitial pneumonia (LIP)
- D - desquamative interstitial pneumonia (DIP)
- R - respiratory bronchiolitis–associated interstitial lung disease (RB-ILD)
- N - non-specific interstitial pneumonia (NSIP)
The first two, AIP and IPF/UIP, have very poor prognosis. The next in the list, COP, is associated with good response to steroids and good prognosis. LIP is more common in women (think "LIPstick"), in contrast to the others, which are either more common in men or have equal gender distribution.
The following two, DIP and RB-ILD, are at extremes of a spectrum, are associated with smoking, and have good response with smoking cessation.
One caveat : The word chronic in the mnemonic should be taken with a grain of salt. Some of the entities may have a subacute presentation, and one, AIP, presents acutely.
- 1. American Thoracic Society/European Respiratory Society International Multidisciplinary Consensus Classification of the Idiopathic Interstitial Pneumonias. This joint statement of the American Thoracic Society (ATS), and the European Respiratory Society (ERS) was adopted by the ATS board of directors, June 2001 and by the ERS Executive Committee, June 2001. Am. J. Respir. Crit. Care Med. 2002;165 (2): 277-304. Am. J. Respir. Crit. Care Med. (link) - Pubmed citation
- 2. Mueller-mang C, Grosse C, Schmid K et-al. What every radiologist should know about idiopathic interstitial pneumonias. Radiographics. 27 (3): 595-615. doi:10.1148/rg.273065130 - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|All Idiopathic Chronic Lung Disease aRe Nonspecific||✗|
|All Idiopathic Chronic Lung Disease aRe Non-specific||✗|