What Causes Blebs On The Lungs? | Why Blebs Form

A “bleb” is a small, thin-walled pocket of air that sits right under the lining on the outside of the lung (the visceral pleura). Many people never feel one. Blebs are often found incidentally on CT scans done for other reasons.

They matter most when a bleb leaks or ruptures. Air can slip into the pleural space (the space between the lung and chest wall) and trigger a pneumothorax, also called a collapsed lung. A plain-language description of blebs, bullae, and their link to pneumothorax is on Baylor College of Medicine’s pulmonary blebs and bullae page.

What A Lung Bleb Is And How It Differs From A Bulla

Blebs are usually small and sit close to the pleura. Bullae are larger air spaces that can form when lung tissue breaks down, often tied to emphysema. Reports sometimes use these terms loosely. What matters clinically is the size, number, and whether the surrounding lung shows other disease.

Some reports also mention “subpleural cysts.” In plain terms, blebs, bullae, and cysts can look similar on a scan because all are air-filled spaces. A useful way to think about it is size and context. A small surface pocket near the apex often gets labeled a bleb. A larger air space, especially with emphysema nearby, often gets labeled a bulla. Cysts can appear with a wider set of conditions and may sit deeper in the lung or show up in a pattern across multiple lobes. If your report lists more than one of these terms, ask which one best matches your scan and whether the surrounding lung looks healthy.

What Causes Blebs On The Lungs? Patterns Doctors Link To Blebs

Blebs do not have one single cause. They tend to show up through a handful of repeat patterns that weaken tissue near the lung surface. These are the most common ones.

Apical Stretch In Tall, Thin Body Types

Blebs are frequently seen near the top (apex) of the lungs. Mechanical forces differ from the bottom to the top, and in some people a tall, slender chest can increase stress at the apex. Clinical summaries of spontaneous pneumothorax often note that primary cases show up more often in young, tall, thin males (NIH NCBI Bookshelf: Spontaneous Pneumothorax).

Smoking And Related Tissue Damage

Smoke exposure can injure small airways and the delicate walls of air sacs. Over time, this can leave areas that stretch, thin, or break down, which can show up as blebs or emphysema-like changes on CT. An NIH NCBI Bookshelf review lists smoking as a common risk factor tied to spontaneous pneumothorax (NIH NCBI Bookshelf: Spontaneous Pneumothorax).

Stopping smoking is one of the few steps that can lower ongoing injury. It will not erase an existing bleb, but it can reduce the chance of new damage and lower recurrence odds after a pneumothorax.

Emphysema And COPD

In emphysema, lung tissue breaks down and leaves larger air spaces behind. Smaller subpleural pockets can appear in the same setting. When a report mentions blebs plus emphysema, clinicians often shift attention to overall lung function and symptom control.

Scarring Near The Pleura

Some blebs sit near areas of prior inflammation or scarring. Past infections, repeated irritation, or localized pleural scarring can create uneven pull on nearby air sacs. A thin-walled pocket can form along that edge.

Inherited Conditions With Lung Cysts

A smaller group of people have blebs or lung cysts linked to inherited conditions. Birt-Hogg-Dubé syndrome is one example; it can involve lung cysts and recurrent pneumothorax risk. MedlinePlus Genetics describes the condition and its lung findings (MedlinePlus Genetics: Birt-Hogg-Dubé syndrome).

Clinicians often think about inherited causes when pneumothorax happens at a young age, episodes recur, a close relative has had pneumothorax, or CT shows a cyst pattern that does not match smoking-related disease.

How A Bleb Can Trigger A Collapsed Lung

A bleb is a fragile pocket of air near the pleura. If its wall tears, air can move out of the lung and into the pleural space. That air changes pressure in the chest, and the lung can recoil away from the chest wall.

The American Thoracic Society’s patient sheet lists common symptoms such as sharp chest pain and shortness of breath, plus how diagnosis is often confirmed with imaging (American Thoracic Society: spontaneous pneumothorax).

Not each pneumothorax is caused by a visible bleb, and not each bleb ruptures. The report is one piece of the picture, not the whole story.

What Your CT Report Can Tell You

Radiology wording often offers clues about likely causes. These details tend to help:

• Location: Apical blebs fit the common primary spontaneous pneumothorax pattern.
• Number And Size: A single small bleb reads differently than many large air spaces.
• Surrounding Lung Notes: Mentions of emphysema, scarring, bronchiectasis, or interstitial change can shift the likely cause.
• Distribution: Basal or multi-lobar cysts can point toward rarer cystic lung disorders.

If you have the report in front of you, scan for any mention of emphysema, scarring, or cysts beyond “blebs.” Those lines often guide the next steps.

Table: Common Causes And Associations Of Lung Blebs

Situation	What’s Happening In The Lung	Clues That Fit
Primary spontaneous pneumothorax pattern	Small subpleural pockets near the lung apex	Young adult, few other CT findings
Tobacco smoking	Airway irritation and air sac wall injury	Smoking history, CT may note emphysema-like change
Emphysema/COPD	Air space enlargement plus surface pockets	Chronic cough, breathlessness, airflow limitation history
Prior infection or pleural scarring	Uneven stress near scarred pleura	CT notes scarring; prior pneumonia or pleurisy history
Severe asthma with air trapping	Big pressure swings that strain weak areas	History of severe flares; air trapping on imaging
Cystic lung disease	Multiple cysts that can rupture and leak	Many cysts across lobes; recurrent pneumothorax
Birt-Hogg-Dubé syndrome	Inherited tendency toward lung cysts	Family history; skin findings; renal screening plan
Connective tissue disorders	Fragile structural proteins in lung tissue	Hypermobile joints; unusual body proportions; family history
Inhalation injury	Local airway and tissue irritation	History of inhaled drugs or chemical exposure

When Blebs Are Found Incidentally

If a CT scan mentions “apical blebs” and you have never had a pneumothorax, many clinicians treat it as a background finding, especially when blebs are small and the rest of the scan is calm.

It still helps to act on what you can control. If you smoke or vape, stopping is worth it. If you get sudden sharp chest pain with breathlessness, treat it as urgent and get checked.

Symptoms That Suggest A Leak

A bleb alone often causes no symptoms. Symptoms show up when air collects around the lung. Common symptoms include sudden sharp chest pain that can feel worse with a deep breath, shortness of breath, and a fast heartbeat. Some people feel shoulder or back pain on the same side. A small pneumothorax can cause mild symptoms and may be found on an x-ray done for another reason.

If chest pain and shortness of breath start suddenly, seek urgent care. A chest x-ray is often enough to confirm pneumothorax and guide treatment.

How Clinicians Sort Out The Underlying Cause

Once pneumothorax is confirmed, clinicians often classify it as primary (no known lung disease) or secondary (a known condition is present). The NCBI Bookshelf review summarizes common conditions linked to secondary cases, such as COPD, cystic fibrosis, and interstitial lung disease.

Tests That Often Follow

• Chest x-ray: Confirms pleural air and estimates size.
• CT scan: Helps when episodes recur or when underlying disease is suspected.
• Pulmonary function testing: Helps when COPD, asthma, or other airway disease is suspected.

Table: When To Seek Care And What Often Happens Next

Scenario	Typical Next Step	Reason
Sudden chest pain with shortness of breath	Urgent evaluation and chest x-ray	Confirms pneumothorax and guides immediate care
Small pneumothorax and stable symptoms	Observation with repeat imaging	Small leaks can seal; repeat imaging checks stability
Larger pneumothorax or stronger symptoms	Aspiration or chest tube	Removes pleural air so the lung can re-expand
Second episode on the same side	CT review and surgeon visit	Recurrence can change the role of procedures
Known COPD or fibrotic lung disease	Specialist visit plus lung function testing	Secondary cases need disease-specific planning
Many cysts or unusual CT pattern	Rare lung disease screening	Looks for inherited syndromes linked to cysts and pneumothorax
Pneumothorax with fever	Infection workup	Rules out infection-related complications
Diving or specialized aviation duties	Specialist clearance	Pressure shifts can raise recurrence odds after a leak

Treatment Options When A Pneumothorax Occurs

Treatment depends on the size of the pneumothorax, symptoms, and stability. Small pneumothoraces may be managed with observation and follow-up imaging. Larger ones may need air removed with a needle or chest tube. If episodes recur, surgical options may include removing visible blebs and reducing recurrence odds with pleurodesis.

Practical Steps After A Bleb Finding

• Stop smoking and vaping: Cuts down ongoing airway injury.
• Know the warning signs: Sudden one-sided chest pain with breathlessness calls for urgent evaluation.
• Share family history: A relative with pneumothorax can change the workup.
• Ask about pressure activities: Scuba diving can be unsafe after pneumothorax unless a specialist clears it.

Takeaway

Blebs often form through apical stress patterns, smoke-related tissue injury, emphysema and other lung diseases, pleural scarring, or inherited cystic lung disorders. Many people live with small blebs and never have symptoms. When pain and breathlessness start fast, the priority is ruling out pneumothorax and treating the leak.