Table 1—

Key features of the idiopathic interstitial pneumonias, as defined by the American Thoracic Society/European Respiratory Society consensus classification 1

Idiopathic pulmonary fibrosisNSIPRespiratory bronchiolitis-associated ILDDIPLIPCryptogenic organising pneumoniaAcute interstitial pneumonia
Histological lesionUIPNSIPRespiratory bronchiolitis ILDDIPLIPOrganising pneumoniaDiffuse alveolar damage
Key histological featuresPatchy subpleural fibrosis with temporal and spatial heterogeneity; fibroblastic foci are typically observed at the leading edge of fibrosisTemporally homogeneous interstitial fibrosis, often with associated mild-to-moderate interstitial infiltratePatchy bronchiolocentric distribution of mild fibrosis, submucosal lymphocytic infiltrate and pigmented macrophages within alveolar ductsDiffuse macrophage accumulation in distal airspaces with accompanying alveolar septal thickening and inflammationDense interstitial lymphoid infiltrate, type II cell hyperplasia and occasional lymphoid folliclesOrganising intraluminal fibrosis with patchy but temporally uniform distribution; underlying lung architecture preservedTemporally uniform lesion with alveolar septal thickening, airspace filling and hyaline membranes; later organisation and fibrosis
Mean age of onset yrs6550–5540–5040–5040–505550
Rate of onsetInsidiousInsidiousInsidiousInsidiousInsidiousSubacuteAcute
PrognosisPoorIntermediateGoodGoodIntermediateGoodVery poor
  • NSIP: nonspecific interstitial pneumonia; ILD: Interstitial lung disease; DIP: desquamative interstitial pneumonia; LIP: lymphocytic interstitial pneumonia; UIP: usual interstitial pneumonia.