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The three features of BHD: skin bumps, lung cysts and kidney tumours | CION Cancer Clinics
Birt-Hogg-Dubé syndrome shows up in three places: harmless skin bumps, air-filled lung cysts that can make a lung collapse, and kidney tumours that can become cancer. Not everyone has all three, and they often appear years apart. This page takes each feature in turn, explains what it looks like and how it is found, and says which one needs the closest watching. At CION Cancer Clinics, our oncologists plan screening and care for families with an inherited cancer syndrome, explained in plain words.
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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
- How do the three features of BHD show up?
- What do BHD skin bumps look like?
- How do lung cysts lead to a collapsed lung?
- What do the kidney tumour words on a report mean?
- Which feature needs what kind of care?
- What this page cannot tell you
- What do people often get wrong about the three features?
- Common questions about the features of BHD
The short answer
How do the three features of BHD show up?
Birt-Hogg-Dubé syndrome, or BHD, shows up in three places: the skin, the lungs and the kidneys. The skin bumps are harmless. The lung cysts are usually silent but can make a lung collapse. The kidney tumours are the only feature that can become cancer, which is why they get the most attention.
They arrive at different times
A collapsed lung often happens in young adult life, sometimes as the very first sign. Skin bumps tend to appear slowly through adulthood and become more numerous with age. Kidney tumours are usually found later, in middle age, though they can appear earlier. So a young person may have only one feature, and their parent may have a different one.
One person rarely shows the whole picture
Some people have all three features. Many have only one or two, and some carriers have none that anyone has noticed. This is why doctors look across the whole family rather than at one person. A brother with a collapsed lung and an uncle with a kidney tumour can together point to BHD.
No single feature proves BHD. A blood test for the FLCN gene is what confirms it.The skin
What do BHD skin bumps look like?
The skin changes are the most visible part of BHD and the least dangerous. None of them turn into cancer.
Fibrofolliculomas
Small, smooth, pale or skin-coloured domes that grow from hair roots. They are the typical BHD bump, and a skin biopsy of one can support the diagnosis.
Skin tags and similar bumps
Soft hanging skin tags on the neck or in the armpits, and other small bumps that look alike to the naked eye. Only a dermatologist can tell them apart reliably.
Where they appear
- Across the nose and cheeks
- On the forehead and behind the ears
- On the neck and upper chest
On darker Indian skin they can be harder to spot, and are often mistaken for acne or warts.
What can be done
Treatment is only for appearance. Laser treatment or careful removal can reduce them, though new bumps often appear later. Leaving them alone is completely safe.
Not sure whether this applies to you?
Ask an oncologistThe lungs
How do lung cysts lead to a collapsed lung?
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Thin air pockets form in the lungs
Most adults with BHD have several small cysts, usually in the lower parts of both lungs. They are seen on a CT scan of the chest, not on an ordinary X-ray.
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Most of the time, nothing happens
The cysts do not usually make you breathless or cough, and lung function tests are often normal. Many people only learn about them after a scan done for another reason.
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A cyst near the surface can burst
If a cyst on the edge of the lung gives way, air leaks into the space around the lung. The lung partly collapses, like a balloon losing air.
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Sudden chest pain and breathlessness follow
The pain is usually sharp and on one side. This needs an emergency department the same day, and a chest X-ray confirms it.
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Treatment, then prevention of the next one
Small collapses may settle with rest. Larger ones need the air drained. Because it tends to happen again in BHD, doctors may suggest a procedure that seals the lung lining to the chest wall.
The kidneys
What do the kidney tumour words on a report mean?
- Oncocytoma
- A kidney tumour that is usually benign, meaning not cancer. It still tends to be removed or watched.
- Chromophobe renal cell carcinoma
- A type of kidney cancer that is common in BHD and usually grows slowly.
- Hybrid oncocytic tumour
- A tumour with features of both of the above. It is the type most typical of BHD, and a strong clue to the diagnosis.
- Clear cell renal cell carcinoma
- The most common kidney cancer in the general population. It is less common in BHD but can occur.
- Multifocal and bilateral
- More than one tumour, and tumours in both kidneys. Both are more likely in BHD than in people without it.
- Kidney-sparing surgery
- An operation that removes the tumour but keeps as much healthy kidney as possible. In BHD this matters, because more tumours may come later.
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Side by side
Which feature needs what kind of care?
Feature
Usual care
Skin bumps
A dermatologist, only if the bumps bother you
Lung cysts with no symptoms
A chest doctor, a baseline CT scan and advice
A sudden collapsed lung
An emergency department, the same day
Kidney tumours
Regular scans and a urologist or cancer surgeon
Being straight with you
What this page cannot tell you
It cannot tell you whether the bumps on your face, a cyst on your scan or a tumour in your kidney are due to BHD. Each of these has many common causes. Facial bumps are very often ordinary acne scars or skin tags. Simple kidney cysts are extremely common and are not the same as kidney tumours.
It cannot read your report
What your specific variant means is a question for the counsellor who ordered the test. A pathology report naming a hybrid tumour is a good reason to ask about BHD, but it is not a diagnosis in itself. Bring your reports to a genetic counsellor or clinical geneticist.
Who this does not apply to
Most people do not need BHD testing. One collapsed lung in a tall, thin young man who smokes, with no family pattern and no cysts on the CT, is common and usually unrelated. A kidney tumour found in older age with no family history rarely points to BHD. Tumour-only gene tests are covered on our targeted therapy pages.
Studies of BHD so far are small, and very few include Indian families.Commonly believed
What do people often get wrong about the three features?
"More skin bumps means a worse form of BHD."
The number of skin bumps does not predict whether you will have a collapsed lung or a kidney tumour. Someone with clear skin needs kidney scans just as much as someone with many bumps.
"Lung cysts will slowly destroy my lungs."
In BHD, the cysts rarely damage breathing over time. This is different from some other cystic lung conditions. The main concern is a sudden collapse, not a gradual loss of lung function.
"A kidney tumour in BHD always means the kidney must come out."
Small tumours are often watched with scans and removed only when they grow. Surgeons try to keep as much kidney as possible, because new tumours may appear years later.
"If my lung collapsed once, it will not happen again."
In BHD, a collapsed lung often comes back, in the same lung or the other one. That is why doctors may suggest preventive treatment after the first episode rather than waiting.
Questions we are asked
Common questions about the features of BHD
Can you have BHD without any skin bumps?
Yes. Some people with BHD never develop visible skin bumps, and others have so few that nobody notices. Studies from East Asia suggest skin changes may be less common in Asian families. A clear face does not rule BHD out if the lung or kidney pattern fits.
Will the skin bumps spread to other people?
No. They are not an infection and cannot pass by touch, sharing towels or living together. They are simply a sign of the inherited gene change. The only way BHD passes on is from a parent to a child through the gene.
Do I need regular chest CT scans for the lung cysts?
Usually not. One CT scan is often done to map the cysts and give a baseline. Repeat scans are generally kept for new symptoms, because the cysts rarely change breathing and extra scans add radiation. Your chest doctor will decide.
How will I know if my lung has collapsed?
Typically a sudden sharp pain on one side of the chest, often worse on breathing in, with breathlessness. It can happen at rest. Go to the nearest emergency department the same day and tell them you have BHD or a family history of collapsed lungs.
Are BHD kidney tumours aggressive?
Most grow slowly, which is why regular scans work well. Some tumour types seen in BHD are not cancer at all. Occasionally a more aggressive type appears, so every tumour is watched or treated according to its size, its growth and what the specialist sees.
Which feature should I worry about most?
The kidneys, because that is where cancer can develop and where regular scans make the biggest difference. After that, know the warning signs of a collapsed lung. The skin bumps are a matter of appearance only and need no medical treatment.
Do the features get worse with age?
Skin bumps usually increase slowly with age. Kidney tumours become more likely through adult life, which is why scans continue for life. Lung cysts may increase a little in number, but the chance of a collapse does not simply rise year on year.
Who should I see first if I think I have one of these features?
Your family doctor or the specialist already treating you, who can refer you to a genetic counsellor. Bring any chest CT reports, kidney pathology reports and a note of relatives with similar problems. The CION helpline can point you to the right clinic.
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 Bookshelf) — Birt-Hogg-Dubé Syndrome
- MedlinePlus Genetics — Birt-Hogg-Dubé syndrome
- National Cancer Institute — Genetics of Kidney Cancer (Renal Cell Cancer) (PDQ) - Health Professional Version
- NHS — Collapsed lung (pneumothorax)
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.
Talk to us
Wondering whether these features in your family are linked?
Tell us who had skin bumps, a collapsed lung or a kidney tumour, and at what age. We will tell you honestly whether a genetic referral is worth making and arrange it if it is. One helpline serves every CION centre.