A spontaneous pneumothorax is a collapsed lung that happens on its own, without any injury or medical procedure causing it. Air leaks from the lung into the space between the lung and the chest wall, creating pressure that prevents the lung from fully expanding. It affects between 7.4 and 18 per 100,000 men each year and 1.2 to 6 per 100,000 women, making it relatively uncommon but far from rare.
Primary vs. Secondary Types
Spontaneous pneumothorax comes in two forms, and the distinction matters because they affect very different people and carry different levels of risk.
Primary spontaneous pneumothorax (PSP) strikes people with no known lung disease. The typical profile is a young adult between 15 and 40, most often a tall, thin male. It’s linked to the rupture of small air-filled sacs called blebs that form near the surface of the lung. Researchers believe rapid chest growth during adolescent growth spurts may contribute to bleb formation, which helps explain why tall young men are the most affected group.
Secondary spontaneous pneumothorax (SSP) happens in people who already have a lung condition. COPD accounts for roughly 70% of these cases. Other causes include cystic fibrosis, asthma, tuberculosis, lung cancer, and various forms of interstitial lung disease. Because the lungs are already compromised, SSP tends to be more dangerous and more difficult to manage. It typically affects older adults.
What Causes the Lung to Collapse
Your lungs stay inflated because of a thin layer of fluid and negative pressure in the pleural space, the narrow gap between the lung and the chest wall. When a bleb or weakened area on the lung surface ruptures, air escapes into that space. As air accumulates, it pushes against the lung and prevents it from expanding normally. In a primary case, this can happen during routine activity or even at rest. There’s no dramatic trigger in most episodes.
Long-term smoking dramatically increases the risk of developing a spontaneous pneumothorax in both men and women. In rare cases, genetic mutations (particularly in the FLCN gene, associated with a condition called Birt-Hogg-Dubé syndrome) and connective tissue disorders like Marfan syndrome or Ehlers-Danlos syndrome play a role.
What It Feels Like
The hallmark symptoms are sudden, sharp chest pain on one side and shortness of breath that comes on without warning. The pain often starts near the shoulder or upper chest and may worsen with deep breathing. In a primary case affecting an otherwise healthy young person, symptoms can range from mild discomfort to significant breathing difficulty depending on how much of the lung collapses.
In secondary cases, even a small collapse can cause severe breathlessness because the lungs were already functioning below full capacity. If you already have a condition like COPD, any additional loss of lung function can feel much more dramatic than the size of the collapse might suggest.
When It Becomes an Emergency
A small percentage of spontaneous pneumothoraces progress to tension pneumothorax, a life-threatening condition where trapped air builds up so rapidly that it shifts the heart and major blood vessels to the opposite side of the chest. Warning signs include severe and worsening breathing difficulty, rapid heart rate, visibly distended neck veins, a bluish tint to the skin, and dangerously low blood pressure. This is a medical emergency requiring immediate treatment.
How It’s Diagnosed and Treated
A chest X-ray is the standard first step. It shows the air pocket and how much of the lung has collapsed. In some cases, a CT scan provides more detail, especially if blebs or underlying lung disease are suspected.
Treatment depends on the size of the collapse and how symptomatic you are. Current British Thoracic Society guidelines state that a primary spontaneous pneumothorax can be managed conservatively (observation alone, no procedure) if you have minimal or no symptoms, regardless of the size visible on imaging. In these cases, the body gradually reabsorbs the trapped air over days to weeks.
When symptoms are more significant or the lung isn’t re-expanding on its own, a chest tube is placed between the ribs to drain the trapped air and allow the lung to reinflate. This typically requires a hospital stay. For larger collapses or persistent air leaks, needle aspiration may be tried first as a less invasive option.
Surgery and Preventing Recurrence
Recurrence is the major long-term concern. Published rates for primary spontaneous pneumothorax range widely, from about 8% to over 50% depending on the study and follow-up period. One study found that 26.5% of patients experienced a recurrence, with the vast majority happening within the first six months after the initial episode. About 78% of those recurrences occurred within three months of hospital discharge.
Surgery is generally recommended when pneumothorax keeps coming back, when there’s a persistent air leak that won’t seal on its own, when imaging shows large blebs likely to rupture again, or when the patient works in a high-risk occupation like aviation. The most common approach is video-assisted thoracic surgery (VATS), a minimally invasive procedure where the surgeon removes the blebs and then roughens or partially removes the lining of the chest wall. This irritation causes the lung to adhere to the chest wall, making future collapse far less likely. Recurrence rates after this combined approach are low.
Recovery and Activity Restrictions
After a first episode treated without surgery, recovery typically takes a few weeks. You’ll have follow-up chest X-rays to confirm the lung has fully re-expanded. Physical activity is generally limited during this period to avoid re-collapse.
Air travel carries specific risks. The lower cabin pressure at altitude causes any trapped gas to expand, which can worsen or trigger a pneumothorax. Guidelines recommend waiting at least seven days after a chest X-ray confirms full resolution before flying. For traumatic pneumothorax, the recommended wait extends to two weeks after confirmed resolution.
Scuba diving poses an even greater concern. The pressure changes involved in diving are far more extreme than in commercial flight, and both diving and altitude exposure have been identified as factors that can provoke a pneumothorax. Most specialists advise against returning to scuba diving after a spontaneous pneumothorax unless definitive surgical treatment has been performed, and even then the recommendation varies.
If you smoke, quitting is the single most impactful thing you can do to lower your risk of a first episode or a recurrence. Smoking cessation substantially reduces the chance of bleb formation and lung tissue breakdown that makes collapse more likely.