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 pattern | Expected course | HRCT findings | |
| Typically reversible | Typically irreversible | ||
| Idiopathic pulmonary fibrosis | Progression is typical | None GGO may evolve into reticulation | Reticulation Honeycombing Traction bronchiectasis Architectural distortion |
| Hypersensitivity pneumonitis | Depends on antigen removal and the presence of fibrosis on HRCT | Findings of acute or subacute hypersensitivity pneumonitis (GGO, consolidation and centrilobular nodules) | Findings of chronic hypersensitivity pneumonitis (reticulation, honeycombing, traction bronchiectasis, emphysema) |
| Respiratory bronchiolitis ILD | Almost always improves with smoking cessation | GGO Centrilobular nodules | Reticulation (rare as a significant finding) GGO that remains after smoking cessation/treatment may represent microscopic fibrosis |
| Desquamative interstitial pneumonia | Majority of patients improve with smoking cessation and/or corticosteroids | GGO (if the patient doesn't stop smoking this may evolve into fibrosis or cystic lucencies) | Cystic lucencies Reticulation Honeycombing GGO that remains after smoking cessation/treatment may represent microscopic fibrosis |
| Langerhans cell histiocytosis | Findings may improve or resolve with smoking cessation | Nodules (if patient doesn't stop smoking these may cavitate and evolve into cysts) Thick-walled cavities | Thin-walled cavities Cysts |
| NSIP | Evolution depends on subtype (cellular versus fibrotic) and is hard to predict on imaging | Findings of cellular NSIP, namely GGO (however this finding is not specific for reversible disease in NSIP) | Findings of fibrotic NSIP (reticulation and traction bronchiectasis) |
| Sarcoidosis | Progression from nodules to fibrosis is rare | Nodules Interlobular septal thickening GGO and consolidation more commonly evolve to fibrosis | Reticulation Honeycombing Cystic airspaces |
| Organising pneumonia | Highly responsive to steroids; relapse may occur | Consolidation GGO | Findings may progress to fibrosis, commonly in an NSIP pattern |
ILD: interstitial lung disease; NSIP: nonspecific interstitial pneumonia; GGO: ground glass opacity.