Pneumothorax is caused by which of the following?

• A. Accumulation of air within the pleural space
• B. Blockage of airways by mucus
• C. Infection of the lung tissue
• D. Inflammation of alveoli

Answer: (A)

Pneumothorax happens when air enters the pleural space, the thin area between the lung and chest wall. That space normally holds a tiny amount of fluid and maintains a negative pressure that helps keep the lung expanded against the chest wall. When air leaks into this space, the pressure balance is upset, the lung can’t stay fully inflated, and it may partially or completely collapse. That’s why the key idea is air accumulating in the pleural space, not problems like mucus blocking airways or infection and inflammation of lung tissue, which cause different conditions (atelectasis or pneumonia) without involving air in the pleural space.