When air enters the pleural space, the pressure in the pleura becomes greater than that in the lungs, and the lung collapses partially or completely. Sometimes most or all of the lung collapses, leading to immediate and severe shortness of breath. The condition is most common in tall men under age 40. Most incidents of simple spontaneous pneumothorax aren't caused by exertion. Some occur during diving or high-altitude flying, apparently because of pressure changes in the lungs.
Most people recover fully.
Complicated spontaneous pneumothorax occurs in people with extensive lung disease. This type of pneumothorax most often results from the rupture of a bulla in older people who have emphysema. Complicated spontaneous pneumothorax may also occur in people with other lung conditions, such as cystic fibrosis, eosinophilic granuloma, lung abscess, tuberculosis, and Pneumocystis carinii pneumonia. Because of the underlying lung disease, the symptoms and outcome are generally worse in complicated spontaneous pneumothorax. Tension pneumothorax is a serious and potentially life-threatening form of pneumothorax.