Day of Giving

Today is the Day of Giving, a day when people come together to support a cause or community. We are developing a BHD patient registry which is a centralised database that collects information about people with BHD. They are particularly useful in the context of rare diseases as they help researchers and clinicians to build a more complete picture of the condition.

View our infographic to find out more. The infographic includes information about our September meeting which has now taken place however there are still ways you can get involved and support the development of the registry.  

Ways to help:

1. Select Myrovlytis Trust on Amazon Smile. We have joined forces with Amazon Smile. Select Myrovlytis Trust as your charity and for each purchase, you make through Amazon Smile, Amazon will donate 0.5% to us.

2. Make a donation through PayPal. Select your charity as the Myrovlytis Trust or use our charity number 1122073 and donate.

3. Sign up for our newsletter to keep up to date with the progress of the registry and associated volunteering opportunities.

4. Share a fundraising idea with us and we can work together to make it a reality. Email us at

5. Share your time and expertise. Do you have a skill in design, translation or other? We would love to know and will get in contact with volunteering opportunities that match your skill. Email us at

6. Share our Twitter and Facebook posts with #GivingTuesday

We want to send out a massive thank you to the BHD community for all your support since the relaunch of BHD Foundation this year.

Lenke’s BHD Story: Pregnancy

Lenke was diagnosed with BHD after a collapsed lung during her pregnancy. In this interview, she discusses her pregnancy, genetic testing, her decision not to have IVF and her yearly BHD dates with her mum at the clinic.

You can watch the interview below.

A transcript of the interview is available here. You can read the transcript in Dutch here.

Why does BHD cause lung cysts?

Birt-Hogg-Dubé syndrome is caused by a mutation in the gene folliculin (FLCN). Unravelling the functions of FLCN has been a focus of research into BHD, because if we can determine how FLCN mutations cause the characteristics of BHD we can potentially reverse them or even prevent them from happening. Lung cysts are a common feature of BHD with cysts being present in up to 80% of patients. An exciting study by Ikue Tai-Nagara and colleagues discovered a new function of folliculin and hypothesised that when lost it may result in lung cyst formation (1).

The body contains different systems, working in harmony to keep us functioning including the cardiovascular and lymphatic systems. The cardiovascular system transports blood throughout the body whereas the lymphatic system collects excess fluid, clears waste, and transports immune cells. The vessels of these two systems are very similar and both are lined with a layer of cells known as endothelial cells. However, throughout the body, the lymphatic and blood vessels are mostly separated. Imagine they are two different train tracks, structurally similar but carrying different cargo.

The research team investigated what would happen if FLCN was knocked out (removed) in endothelial cells. They studied mouse models at different developmental stages and found that knocking out FLCN in mice that were still developing resulted in enlarged and blood-filled lymphatic vessels. Examining both the lymphatic vessels and blood vessels under a microscope they observed that the lymphatic vessels were developing offshoots towards veins (the blood vessels that transport blood from the organs to the heart) and the veins were developing offshoots towards the lymphatic vessels. It appeared that there was an attraction between the two systems that had not previously been present. Additionally, the lymphatic endothelial cells were dividing rapidly which was the likely cause for the enlargement of the lymphatic vessels.

Next, the researchers investigated why knocking out FLCN caused a change in the relationship between the lymphatic vessels and veins and one key gene stood out. PROX1 controls the development of lymphatic endothelial cells. In mice where FLCN was knocked out not only was PROX1 expressed in the lymphatic endothelial cells (where it should be) but it was also inappropriately expressed in the endothelial cells of the veins. The significance of this expression was highlighted when PROX1 was deleted from the endothelial cells and the characteristics of the vessels normalised.

Next, they needed to connect how knocking out FLCN caused PROX1 expression to increase. They focused on TFE3, which is well documented as being regulated by FLCN (find out more in our recent blog post). Firstly they found that TFE3 was highly expressed in the endothelial cells of the FLCN knockout mice. They then looked at human endothelial cells and found that knocking down FLCN increased PROX1 and that this could be reversed by also knocking down TFE3. They also showed that TFE3 bound and regulated the PROX1 gene. Therefore, when FLCN was knocked down and could no longer regulate TFE3, PROX1 increased resulting in changes to the lymphatic vessels and veins.

So, what has all this got to do with the lungs? The final experiment involved looking at lung samples from three BHD patients. The samples were compared with normal lung specimens and non-BHD cyst-filled lungs. Significantly, only the BHD lung specimens showed evidence of lymphatic vessels filled with blood, inappropriate PROX1 expression and increased TFE3 expression. This suggests that the structural changes in the lungs such as cysts could be linked with the disruption of the lymphatic and cardiovascular systems.

Altogether this research demonstrates a new role of folliculin as a gatekeeper of the lymphatic and cardiovascular system. New research is on the horizon looking further into how lung cysts form and how these pathways can be targeted therapeutically to improve the lung symptoms associated with BHD.


1.      Tai-Nagara I, Hasumi Y, Kusumoto D, Hasumi H, Okabe K, Ando T, et al. Blood and lymphatic systems are segregated by the FLCN tumor suppressor. Nat Commun [Internet]. 2020 Dec 1 [cited 2021 Oct 27];11(1). Available from: /pmc/articles/PMC7725783/

2021 BHD Symposium Report

October saw the first ever virtual BHD Symposium, and we were delighted to welcome speakers, chairs and 293 attendees from across the globe for two days of research updates and discussion. In this report we highlight the current research conducted into BHD and look to the future for what this means for those who have been diagnosed with the condition.

BHD Diagnosis and Management 

Raising awareness of BHD was a prominent theme throughout the symposium. There were discussions about involving the media, creating accessible resources and the patient panel together emphasised the importance of healthcare professionals recognising and diagnosing BHD. It was wonderful to see active research carried out on how to support doctors to identify the symptoms and investigate the possibility of BHD. One study found that 1 in 7 pneumothoraces were familial and BHD was the most common known cause (1). It was suggested that people who have a spontaneous pneumothorax could have CT scans to look for BHD. As BHD associated pneumothoraces tend to first occur in 20/30s this also means if BHD is diagnosed from the CT scan, kidney screening can start early. Currently kidney cancer screening is recommended for all BHD patients from the age of 20, and research has so far not identified any folliculin (FLCN) variants that predispose to a specific BHD symptom (2). Avgi Andreou, one of our early career talk winners, is investigating pathogenic variants in cancer susceptibility genes in kidney cancer and we can’t wait to blog about her research when it’s published. It’s inspiring to see a new generation of researchers dedicated to improving outcomes for those diagnosed with BHD.

It was also interesting to hear how BHD presents differently in different populations and the challenges of identifying whether this is due to lack of awareness or difference in genetics. Lung symptoms appear to be the most common presentation of BHD in Asian patients whereas the skin symptoms appear to be less common compared with Caucasian patients.  Additionally, a pilot study investigated the genetics of 15 Indian BHD families. One particularly interesting aspect was four of these families, although presenting clinically with BHD, had no identifiable pathogenic mutation. At the BHD Foundation we often get asked whether you can have BHD without a folliculin variant, and the answer appears to be yes; there may be other genes involved that we do not know about. This is why the BHD Foundation is investigating the creation of clear diagnostic guidelines in the presence and absence of FLCN mutations.

Several talks discussed the management of the symptoms of BHD. A novel technique to prevent recurrent pneumothoraces, called total pleural covering was described. Pleurodesis is the most common treatment to prevent recurrent pneumothorax (3). Surgeons irritate the lining of the lung causing it to stick to the chest. Total pleural covering on the other hand involves a mesh network to keep the lung inflated. It will be interesting to see what techniques are adopted by surgeons over the next few years. It was also exciting to hear ongoing research into fibrofolliculomas and kidney cancer. Research into the structure and formation of fibrofolliculomas has the potential to lead to new topical treatments. Additionally the identification of drugs to treat kidney cancers could prevent the need for recurrent surgeries. Lastly in Germany BHD patients are also offered colon cancer screening from the age of 40. A recent paper found that there may be an increased risk of early onset colon cancer in the BHD population (4). Further research into this is required and it is one of the many questions we hope our registry, that we are setting up will be able to answer.

Understanding Folliculin

There were several talks focusing on trying to understand what FLCN is doing inside cells that contributes to the manifestations seen in BHD. This knowledge is important so that it can guide the development of new therapies to treat the symptoms of BHD. Many talks centred around the kidneys and the role FLCN as a tumour suppressor i.e., the lack of FLCN contributes to tumour growth and therefore kidney cancer development. One of the major pathways studied in the context of FLCN and BHD is the mTOR signalling pathway and the transcription factors TFEB and TFE3 (5,6). Loss of FLCN leads to constitutive activation of TFEB and TFE3 which drive tumour progression; further understanding of this pathway was the focus of several talks.

However, FLCN is also involved in many cellular pathways, on which other speakers presented data demonstrating other roles for FLCN in cancer development (7). Iris Glykofridis, one of our early career talk winners described her work showing that a lack of FLCN has the potential to alter immune responses (8). This is important as the immune system can inhibit tumour growth and as such, the immune system is often modulated in cancer. The role of FLCN in epidermal growth factor receptor (EGFR) signalling was also discussed. EGFR is often overexpressed in cancers and results in a number of so-called ‘hallmarks of cancer’ such as increased cell growth. Loss of FLCN led to an increase in EGFR signalling and could therefore contribute to cancer progression (9). Another important change that cancer cells undergo to favour their growth is alteration of metabolism to increase the amount of available energy (known as the Warburg effect). Data presented at the BHD symposium demonstrated that a loss of FLCN increased a key enzyme important in the switch to this altered metabolism and suggested that inhibition of this enzyme could inhibit tumour progression (10).  

Although kidney cancer is the most serious manifestation of BHD from a clinical perspective and thus warrants a lot of research, it was fantastic to see research presented that focused on the role FLCN plays in the development of lung cysts (11). This research was centred around the FLCN – TFE3 signalling axis, although outside of the role of FLCN as a tumour suppressor. This highlights the complexity of the molecular biology of FLCN and the need to fully understand the many roles FLCN plays and how this contributes to BHD pathogenesis.

The BHD Voice

As well as hearing from the researchers It was wonderful to hear from those living with BHD. They discussed the challenges they faced to reach a diagnosis and the resources that could be useful for them. The BHD Foundation are working on a number of projects that we hope to bring to the BHD community in the near future, including a BHD patient registry, virtual coffee mornings and a global BHD day.

We asked you what you thought and this is what you said:

The BHD Symposium reinforced the importance of unifying the BHD community and working together to raise awareness and hopefully one day find a cure for BHD. We are looking forward to hosting the next BHD Symposiumhopefully both in person and virtually and can’t wait to see you there.


1.        Grimes HL, Holden S, Babar J, Karia S, Wetscherek MT, Barker A, et al. Combining clinical, radiological and genetic approaches to pneumothorax management. Thorax [Internet]. 2021 Jun 18 [cited 2021 Oct 27]; Available from:

2.        Are there pathogenic variants of FLCN that do not cause kidney cancer, thus avoiding a requirement for lifelong surveillance? – Birt-Hogg-Dubé Syndrome [Internet]. [cited 2021 Oct 27]. Available from:

3.        Mizobuchi T, Kurihara M, Ebana H, Yamanaka S, Kataoka H, Okamoto S, et al. A total pleural covering of absorbable cellulose mesh prevents pneumothorax recurrence in patients with Birt-Hogg-Dubé syndrome. Orphanet J Rare Dis [Internet]. 2018 May 15 [cited 2021 Oct 27];13(1). Available from:

4.        Is Birt-Hogg-Dubé Syndrome linked with colon cancer? – Birt-Hogg-Dubé Syndrome [Internet]. [cited 2021 Oct 27]. Available from:

5.        Folliculin: A Regulator of mTOR Signaling – Birt-Hogg-Dubé Syndrome [Internet]. [cited 2021 Oct 27]. Available from:

6.        Exploring a molecular link between Birt-Hogg-Dubé Syndrome and Tuberous Sclerosis. – Birt-Hogg-Dubé Syndrome [Internet]. [cited 2021 Oct 27]. Available from:

7.        Folliculin: Functions Independent of mTOR and AMPK – Birt-Hogg-Dubé Syndrome [Internet]. [cited 2021 Oct 27]. Available from:

8.        Disruption of Folliculin Induces the Activation of Interferon Response Genes in a Human Renal Cell Model – Birt-Hogg-Dubé Syndrome [Internet]. [cited 2021 Oct 27]. Available from:

9.        Laviolette LA, Mermoud J, Calvo IA, Olson N, Boukhali M, Steinlein OK, et al. Negative regulation of EGFR signalling by the human folliculin tumour suppressor protein. Nat Commun 2017 81 [Internet]. 2017 Jun 28 [cited 2021 Oct 27];8(1):1–14. Available from:

10.      A New Role for Folliculin in Cancer Prevention – Birt-Hogg-Dubé Syndrome [Internet]. [cited 2021 Oct 27]. Available from:

11.      Tai-Nagara I, Hasumi Y, Kusumoto D, Hasumi H, Okabe K, Ando T, et al. Blood and lymphatic systems are segregated by the FLCN tumor suppressor. Nat Commun [Internet]. 2020 Dec 1 [cited 2021 Oct 27];11(1). Available from: /pmc/articles/PMC7725783/

New BHD Case Reports

This summer saw the publication of two new Birt-Hogg-Dubé Syndrome (BHD) case reports. A case report is a published research paper discussing one patient’s story. This is particularly beneficial for rarer conditions such as BHD as clinicians can learn from these cases and potentially reach a diagnosis more easily.

In the first case, a 52-year-old Caucasian man presented to the dermatologist with multiple skin complaints (1). For several years he had been developing sebaceous cysts which required minor surgery to remove. He also had numerous 0.2-0.4cm white facial bumps on his nose, jaw and forehead; they neither caused him discomfort nor had been previously commented on in his medical records. However, it was these bumps that raised the possibility to the dermatologist that there may be a genetic basis to this condition, and a skin biopsy showing fibrofolliculomas followed by genetic testing confirmed BHD.

Although there was now an answer for the fibrofolliculomas the cause of the recurrent sebaceous cysts was uncertain. Sebaceous cysts are rarely seen in BHD but they can occur, raising the question of whether sebaceous cysts are a less common skin manifestation of BHD. A case study is not able to answer this question because you need several patients to determine whether a symptom is a correlation (occurs at the same time as the syndrome but is not caused by the syndrome) or causation (the syndrome directly causes the symptom). This is why we are very excited to get the BHD registry up and running, where data can be collected from lots of BHD individuals, and we can answer questions such as ‘Are sebaceous cysts a symptom of BHD?’. 

The second case was a 26-year-old Asian woman with a history of recurrent pneumothorax (2). After the 5th pneumothorax in 8 months and the discovery that it ran in the family, she was investigated further. A scan showed cystic changes in the lung and examination of the skin showed multiple white-domed bumps on the neck and ears in keeping with fibrofolliculomas. It has been previously noted that the skin manifestations of BHD are less common in the Asian community compared with the Caucasian community and whether it is under-diagnosed or there is a genetic difference is yet to be determined.  The patient and her family underwent genetic testing which showed a mutation in her FLCN gene inherited from her mother’s side. She and her family members were diagnosed with BHD.

Both these cases highlight just how important it is for respiratory physicians and dermatologists to have the tools to recognise and diagnose BHD. In the first case, the patient had no symptoms of BHD except for the fibrofolliculomas and no significant family history. Therefore this diagnosis was dependent on the dermatologists recognising the skin symptoms alone. In the second case, it was the recurrent pneumothorax that led the respiratory physicians to question why they continued to reoccur and genetic testing.

The BHD Foundation is working to raise awareness of BHD among clinicians and are excited to be running the first virtual BHD symposium in 2 weeks. Find out more here.


 1.         Medhus E, Siegel M, Boscia J. A Unique Presentation of Birt-Hogg-Dube Syndrome. Cureus [Internet]. 2021 Aug 16 [cited 2021 Oct 6];13(8). Available from: /pmc/articles/PMC8443214/

2.          Lu Y-R, Yuan Q, Liu J, Han X, Liu M, Liu Q-Q, et al. A rare occurrence of a hereditary Birt-Hogg-Dubé syndrome: A case report. World J Clin Cases [Internet]. 2021 Aug 26 [cited 2021 Oct 6];9(24):7123. Available from: /pmc/articles/PMC8409184/

BHD Toolkit: What is a mutation?

When researchers talk about BHD mutations they use phrases such as ‘Missense, Deletion and Frameshift’. But what do these words mean, how do mutations occur and what type of BHD mutation do you have? In today’s BHD toolkit we explore these terms and explain the different types of genetic mutations.

DNA carries all your genetic information, in the form of a code. Imagine a computer code tirelessly running to make sure everything is working smoothly. It is made up of components called nucleotides and it is the order of these nucleotides that determines the bodies programming in other words which proteins are made. Every 3 nucleotides encode for one amino acid, the building blocks of protein, so a change in the nucleotide sequence, can alter the amino acids which ultimately changes the final protein product. This change is called a mutation. Mutations can be caused by the environment or inherited from family members. In BHD, the change in nucleotide sequence and resulting amino acids changes the function of folliculin (FLCN). Several types of FLCN mutations have been identified across the world.

Types of genetic mutation found in BHD

* Splice-site mutation diagram

It can be surprising how one nucleotide change can have the same impact as a large deletion of genetic material, however, going back to our computer analogy it just takes one mistake in the code to stop the programme from working. Therefore, any changes to FLCN which stops it from functioning will result in BHD.

Currently, the management for BHD patients is the same regardless of mutation type but scientists are interested in discovering whether certain mutations are associated with particular BHD characteristics. This could lead to a patient-tailored treatment plan including kidney cancer screening.

In our next BHD Toolkit, we will be diving further into specific FLCN mutations, how to understand your sequencing results and what to expect when you see a clinical geneticist.

Charlotte’s BHD Story: Kidney Cancer

Charlotte lives in Denmark and was diagnosed with BHD after multiple lung collapses in the family.  Kidney screening revealed a mass on her kidney resulting in surgery which didn’t go as expected. Watch Charlotte’s inspiration interview as she discusses how it felt to find a mass on her kidney, the treatment she underwent and how she strongly believes that in most cases BHD does not affect your quality of life.  

The transcript is available here. We also want to thank Charlotte for her help with the Danish translation of the transcript available here.

A New Role for Folliculin in Cancer Prevention

We are excited to be sharing with you a recently published paper by Woodford et al., exploring the reason why the loss of folliculin (FLCN), the gene mutated in Birt-Hogg-Dubé syndrome (BHD), drives tumour development.

Cancer cells have characteristics that allow them to grow and replicate uncontrollably. One of these is the deregulation of cellular metabolism, in other words, cancer cells can change how they get their energy. To produce energy cells normally break up glucose to produce pyruvate which then interacts with oxygen and releases carbon dioxide (CO2). If there is limited or no oxygen pyruvate is converted to lactate instead. However, cancer cells will rapidly take up glucose and convert pyruvate into lactate, even in the presence of oxygen, which is beneficial for the cancer cell. This shift in cellular metabolism is known as the Warburg effect and is driven by Lactate Dehydrogenase A (LDHA), the enzyme which converts pyruvate into lactate. Interestingly, loss of FLCN has previously been shown to increase LDHA activity. Woodford et al., examined this relationship further and investigated whether LDHA could be targeted to treat Kidney cancer.

Several different experiments were undertaken to characterise the relationship between FLCN and LDHA. Detailed examination of the FLCN protein in a kidney cell line showed that FLCN interacted with 114 different proteins including LDHA and that high FLCN expression reduced LDHA activity. To determine how FLCN reduced LDHA activity the relationship between LDHA and its cofactor (a small molecule needed for LDHA activity) was examined. High levels of FLCN reduced the binding between LDHA and its cofactor likely through alteration of LDHA’s structure thereby reducing the activity of LDHA. Taken together these results demonstrate a new role for folliculin as a binding partner and inhibitor of LDHA.  

Next Woodford et al., examined the significance of this finding in cancer cells. 13 cell lines, including a kidney cell line, showed a metabolic shift and hyperactivity of LDHA. 11 of these cell lines also showed a dissociation between FLCN and LDHA suggesting that the inhibitory effects of FLCN are lost in many cancer cell lines.

The creation of targeted therapies against LDHA has always been an appealing area of investigation for cancer treatments, however creating a target that is specific to LDHA has been challenging because there are other similar proteins. The discovery of FLCN as an inhibitor of LDHA creates a new opportunity for such therapies. Firstly, Woodford et al, showed that FLCN binds specifically to LDHA and none of its similar proteins. They then identified the specific region of the FLCN protein which binds to LDHA.  They produced a series of peptides (a chain of amino acids which is the building blocks of proteins) derived from FLCN to target LDHA based on their findings of how FLCN binds to LDHA. These peptides were tested in normal kidney cells in vitro and those that were taken up by the cells and reduced LDHA activity were selected for further tests. They then examined the response to the peptides in a kidney cancer cell line. One of the peptides named FLCN-10 was able to bind to LHDA and this resulted in cancer cell death. Next tissue samples from a kidney cancer of a BHD patient were treated with FLCN-10. FLCN effectively reduced LDHA activity in the kidney cancer cells.  

Altogether Woodford et al., have demonstrated a new role of FLCN as an inhibitor of LDHA. It binds to LDHA and regulates its activity. Therefore, in BHD, loss of FLCN results in LDHA hyperactivity resulting in the Warburg effect which is beneficial for cancer cells.  An understanding of this interaction between FLCN and LDHA meant Woodford et al., were able to create a folliculin derived peptide which bound to LDHA and inhibited its activity. This discovery could pave the way for a new LDHA targeted cancer treatment not only for BHD patients but other cancer patients as well.

We are sorry that the paper is currently not freely available. Please message us if you have any further questions at


1. Woodford MR, Baker-Williams AJ, Sager RA , Backe SJ , Blanden AR, Hashmi F, et al. The tumor suppressor folliculin inhibits lactate dehydrogenase A and regulates the Warburg effect. Nat Struct Mol Biol [Internet]. 2021 Aug 1 [cited 2021 Sep 3];28(8):662–70. Available from: