What are the causes of lung fibrosis?

The causes of lung fibrosis

Apical lung fibrosis:

• TB
• Extrinsic allergic alveolitis (farmer's lung; bird fancier's disease)
• Ankylosing spondylitis
• Allergic bronchopulmonary aspergillosis
• Radiation
• Sarcoidosis
• Histiocytosis lX

Fibrosis predominantly affecting the upper zone:

• Extrinsic allergic alveolitis 
• Coal worker's pneumoconiosis/ progressive massive fibrosis 
• Silicosis 
• Sarcoidosis 
• Histiocytosis 
• Tuberculosis 
• Ankylosing spondylitis (rare)
• Cyclophosphamide induced fibrosis 

Fibrosis predominantly affecting the lower zone: 

• Cryptogenic fibrosing alveolitis 
• Most connective tissue disorders e.g. rheumatoid arthritis, systemic sclerosis (except Ankylosing spondylitis)
• Drug-induced: amiodarone, bleomycin, methotrexate 
• Asbestosis 
• As a late complication of aspiration pneumonia