Important to differentiate between conditions causing predominantly upper or lower zone fibrosis

• The more common causes tend to affect the lower zones (drugs, IPF)

Fibrosis predominately affecting the lower zones

• drug-induced: amiodarone, bleomycin, methotrexate
• asbestosis
• idiopathic pulmonary fibrosis
• most connective tissue disorders (except ankylosing spondylitis) e.g. SLE

Acronym for causes of upper zone fibrosis:

CHARTS

• C - Coal worker's pneumoconiosis
• H - Histiocytosis/ hypersensitivity pneumonitis
• A - Ankylosing spondylitis
• R - Radiation
• T - Tuberculosis
• S - Silicosis/sarcoidosis