Medical Oncologist
CION Cancer Clinics
Lung cysts and a collapsed lung in BHD | CION Cancer Clinics
Most adults with an FLCN fault have small air-filled cysts in their lungs. They are not cancer and rarely affect breathing. Their one real risk is that a cyst bursts and a lung collapses, which is far more common in BHD than in other people and often happens more than once. This page explains the cysts, the warning signs, and what treatment involves. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- Why does an FLCN fault cause lung cysts?
- When should a collapsed lung make a doctor think of BHD?
- What happens when a lung collapses in BHD?
- What do the lung words on your report mean?
- What can this page not tell you?
- What do families get wrong about BHD lung cysts?
- Common questions about lung cysts and BHD
The short answer
Why does an FLCN fault cause lung cysts?
An FLCN fault weakens the tissue at the edges of the tiny air sacs in the lungs. Over time, small thin-walled air pockets called cysts form, mostly in the lower parts of both lungs. They are not cancer and they do not turn into cancer.
Most carriers have them, few notice them
Most adults with Birt-Hogg-Dubé syndrome, or BHD, have cysts that show up on a CT scan of the chest. Breathing is usually normal, and lung function tests are usually normal too. Many people only learn they have cysts when a scan is done for another reason.
The real risk is a collapsed lung
A cyst near the lung's surface can burst. Air then leaks into the space around the lung, and the lung partly collapses. Doctors call this a pneumothorax. It is much more common in BHD than in other people, and it often happens more than once. For some families, a collapsed lung is the very first sign that BHD is present.
Lung cysts in BHD are not a cancer and do not raise the risk of lung cancer.Clues worth noticing
When should a collapsed lung make a doctor think of BHD?
Most collapsed lungs have nothing to do with genes. A few patterns make BHD worth asking about.
It runs in the family
Two or more relatives have had a collapsed lung with no clear cause. This is one of the strongest clues. Ask older relatives directly, because a collapsed lung decades ago is often forgotten or never named.
Cysts on the CT scan
Several cysts in the lower lungs, especially near the centre of the chest, point towards BHD. Your chest doctor will recognise the pattern.
Often seen with
- Normal breathing tests
- Cysts in both lungs
- No history of heavy smoking
Skin bumps or kidney tumours
Small pale bumps on the face, or a relative with kidney tumours at a young age, alongside a collapsed lung, is a strong reason to ask for a genetics referral.
Mistaken for old TB
In India, cysts and a collapsed lung are sometimes first put down to past tuberculosis. If TB tests are negative and the pattern fits, BHD is worth raising.
Only a doctor can tell these apart. Do not stop any TB treatment on your own.Not sure whether this applies to you?
Ask an oncologistIf it happens
What happens when a lung collapses in BHD?
Assessment in the emergency room
A chest X-ray or CT confirms the collapse and shows how large it is. Tell the team you have BHD or lung cysts.
Letting the air out
A small collapse may settle with rest and oxygen. A larger one needs a needle or a thin tube placed in the chest to let the trapped air escape.
Stopping it happening again
Because a second collapse is common in BHD, your chest surgeon may suggest a procedure that seals the lung to the chest wall. This is called pleurodesis.
Recovery and follow-up
Your team will tell you when it is safe to fly, lift heavy things or return to sport. Keep the discharge summary with your genetics report.
On your scan report
What do the lung words on your report mean?
- Cyst
- A thin-walled pocket of air inside the lung. In BHD these are harmless unless one bursts.
- Pneumothorax
- A collapsed lung, when air leaks out of the lung into the space around it.
- Spontaneous
- Happening without an injury. Most collapsed lungs in BHD are spontaneous.
- Recurrent
- Happening again. A recurrent pneumothorax is common in BHD and is one reason to consider pleurodesis.
- Pleurodesis
- A procedure that makes the lung stick to the inside of the chest wall, so it cannot collapse the same way again.
- High-resolution CT
- A detailed chest scan that shows small cysts clearly. It is how cysts are usually found.
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One thing that cannot wait
Sudden sharp chest pain on one side, with breathlessness that comes on quickly, can be a collapsed lung. Go to the nearest emergency department the same day and say you have lung cysts or BHD. Do not wait to see if it settles, and do not board a flight. If you are already abroad or travelling, get checked before you fly home.
Being straight with you
What can this page not tell you?
It cannot tell you whether your cysts or your collapsed lung are caused by BHD. That needs a chest doctor who has seen your scans and a genetic counsellor who has drawn your family tree. What your specific variant means is a question for the counsellor who ordered the test.
It cannot say whether you are safe to fly or dive
Advice on flying, scuba diving and heavy exercise depends on how many cysts you have, whether a lung has collapsed before and how recently. Your chest doctor gives that advice for you personally.
Who this does not apply to
Most people who have a collapsed lung do not have BHD. A tall, thin young smoker with one collapsed lung and a normal CT usually does not need a genetic test. Other lung conditions also cause cysts, and your doctor will think about those too.
It cannot replace the kidney plan
If BHD is confirmed, the lung story is only part of it. The kidney scans matter more over a lifetime, and relatives need to be offered a test. A counsellor can explain this to the family in Telugu, and help you decide who to tell first.
Commonly believed
What do families get wrong about BHD lung cysts?
"Lung cysts mean my lungs are failing."
In BHD, breathing is usually normal and the cysts rarely grow into a problem on their own. The lungs keep working well for most carriers throughout life.
"The cysts need to be removed."
They do not. Surgery is only needed if a lung collapses, and even then the aim is to stop another collapse, not to take out every cyst.
"A collapsed lung once means it will not happen again."
In BHD, a second collapse is common. That is why chest surgeons often discuss sealing the lung after the first episode.
"The lung problem is the dangerous part of BHD."
A collapsed lung is frightening and needs urgent care, but it is treatable. The kidney tumour risk is the part that needs lifelong scans, so do not let the lung story crowd it out.
Questions we are asked
Common questions about lung cysts and BHD
Can I fly if I have BHD lung cysts?
Most carriers with cysts fly without trouble. The risk rises if a lung has recently collapsed. Ask your chest doctor before long flights, and never fly with chest pain or sudden breathlessness until you have been checked.
Is scuba diving safe?
Diving is usually discouraged for people with lung cysts, because pressure changes under water can make a cyst burst. A collapse deep under water is far more dangerous than one on land. Talk to your chest doctor before you dive.
Does smoking make the cysts worse?
Smoking damages the lungs further and raises the chance of a collapsed lung in everyone. It also raises kidney cancer risk. Stopping is one of the most useful things a carrier can do.
Do I need repeated chest scans?
Usually not. A chest CT is often done once to see how many cysts are present. After that, scans are repeated only if you have symptoms. Kidney scans are the ones that need to happen regularly.
Can children have BHD lung cysts?
Cysts and collapsed lungs are uncommon in childhood and usually appear in adult life. Testing a child for BHD is normally discussed with a counsellor first, and most families wait until the child is old enough to decide.
Can I play sport or lift weights?
Most carriers can stay active. Very heavy straining may add some risk, but the evidence is thin. Ask your doctor what suits you, especially in the weeks after a collapse or a chest procedure.
Is pregnancy riskier with lung cysts?
A collapsed lung during pregnancy has been reported in BHD, but it is uncommon. Tell your obstetrician about the diagnosis early so the team knows what to look out for during pregnancy and delivery.
Who should I see first?
A chest doctor for the lungs, a urologist for the kidney scans and a genetic counsellor for the family. Call the CION helpline if you are not sure where to begin, and we will help you arrange the right appointments.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- GeneReviews (NCBI) — Birt-Hogg-Dubé Syndrome
- MedlinePlus Genetics — Birt-Hogg-Dubé syndrome
- NHS — Collapsed lung (pneumothorax)
- MedlinePlus Genetics — FLCN gene
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
The FLCN gene: what it does and why it mattersThe whole of BHD, skin, lungs and kidneysFLCN mutation: which cancers and what riskThe kidney risk that matters most over a lifetimeSurveillance for FLCN carriersWhich checks carriers need, and which they can skipTesting the family for FLCNWho else in the family should be offered a test
Talk to us
Has someone in your family had a collapsed lung more than once?
Tell us who was affected and what the scans showed. We will help you work out whether a genetics referral makes sense and arrange it if it does. One helpline serves every CION centre.