Expansion
Upper zone and lower zone causes have distinct differentials
Expansion
Upper zone - CHARTS
- C - Coal worker’s pneumoconiosis
- H - Hypersensitivity pneumonitis (extrinsic allergic alveolitis)
- A - Ankylosing spondylitis
- R - Radiation
- T - Tuberculosis
- S - Sarcoidosis, silicosis
Lower zone
- Idiopathic pulmonary fibrosis
- Asbestosis
- Connective tissue disease: rheumatoid arthritis, systemic sclerosis, lupus
- Drugs: amiodarone, methotrexate, nitrofurantoin, bleomycin
Idiopathic pulmonary fibrosis shows the usual interstitial pneumonia pattern: subpleural, basal, honeycombing with traction bronchiectasis and temporal heterogeneity. It carries a poor prognosis and is treated with antifibrotics rather than immunosuppression, which distinguishes it importantly from the inflammatory interstitial diseases.
Sarcoidosis produces non-caseating granulomas with bilateral hilar lymphadenopathy, and is staged by the balance of nodal and parenchymal disease.
Physiologically all produce a restrictive defect with reduced transfer factor and exercise desaturation.