May Be Caused by

 Common

Atelectasis

Bronchogenic carcinoma

Invasive thymoma

Large unilateral pleural effusion

Mesothelioma

Pectus excavatum

Pneumonectomy

Pulmonary lobectomy

Tension pneumothorax

Teratoma

Thymolipoma

Unilateral emphysema

 Uncommon

Agenesis of one lung

Bronchiolitis obliterans

Bronchogenic cyst

Congenital lobar emphysema

Cystic adenomatoid malformation

Diaphragmatic hernia

Giant bulla

Giant pulmonary cyst

Hypoplasia of one lung

Isoniazid cyst

Occluded bronchus

Partial absence of pericardium

Pulmonary interstitial emphysema

Swyer-James syndrome

Unilateral pulmonary fibrosis