Abstract
Tension pneumothoraces in patients with underlying lung or pleural disease or both may appear atypical on x-ray films. The pneumothorax may be localized and resemble a cyst or bleb or may be small enough to seem insignificant. Since clinical evaluation can be misleading if the pneumothorax is localized and the trachea remains midline, recognition of atypical patterns on the x-ray films is important for emergency treatment.