Expected course of common diffuse lung diseases, including a list of high-resolution computed tomography (HRCT) findings for each disease that are typically reversible versus irreversible

Disease or patternExpected courseHRCT findings
Typically reversibleTypically irreversible
Idiopathic pulmonary fibrosisProgression is typicalNone
GGO may evolve into reticulation
Traction bronchiectasis
Architectural distortion
Hypersensitivity pneumonitisDepends on antigen removal and the presence of fibrosis on HRCTFindings of acute or subacute hypersensitivity pneumonitis (GGO, consolidation and centrilobular nodules)Findings of chronic hypersensitivity pneumonitis (reticulation, honeycombing, traction bronchiectasis, emphysema)
Respiratory bronchiolitis ILDAlmost always improves with smoking cessationGGO
Centrilobular nodules
Reticulation (rare as a significant finding)
GGO that remains after smoking cessation/treatment may represent microscopic fibrosis
Desquamative interstitial pneumoniaMajority of patients improve with smoking cessation and/or corticosteroidsGGO (if the patient doesn't stop smoking this may evolve into fibrosis or cystic lucencies)Cystic lucencies
GGO that remains after smoking cessation/treatment may represent microscopic fibrosis
Langerhans cell histiocytosisFindings may improve or resolve with smoking cessationNodules (if patient doesn't stop smoking these may cavitate and evolve into cysts)
Thick-walled cavities
Thin-walled cavities
NSIPEvolution depends on subtype (cellular versus fibrotic) and is hard to predict on imagingFindings of cellular NSIP, namely GGO (however this finding is not specific for reversible disease in NSIP)Findings of fibrotic NSIP (reticulation and traction bronchiectasis)
SarcoidosisProgression from nodules to fibrosis is rareNodules
Interlobular septal thickening
GGO and consolidation more commonly evolve to fibrosis
Cystic airspaces
Organising pneumoniaHighly responsive to steroids; relapse may occurConsolidation
Findings may progress to fibrosis, commonly in an NSIP pattern

ILD: interstitial lung disease; NSIP: nonspecific interstitial pneumonia; GGO: ground glass opacity.