Should People Who Have a Collapsed Lung be Tested for BHD?

Birt-Hogg-Dubé syndrome (BHD) is an inherited condition associated with mutations in the gene folliculin (FLCN). It is characterised by skin lesions called fibrofolliculomas, lung cysts, collapsed lungs and an increased risk of kidney cancer. As different people may have different symptoms, the diagnosis of BHD may be missed. It is therefore thought that BHD is underdiagnosed. Early diagnosis of BHD is important to identify and treat any kidney cancer as early as possible. Finding effective ways to diagnose BHD could help reduce any future burden of kidney cancer.

A new study has been published looking at the prevalence of BHD among people who have a collapsed lung for no apparent reason (e.g. not as a result of a direct injury). This is called a primary spontaneous pneumothorax (PSP). Currently, a CT scan is not routinely performed on people who have a PSP. However, it is thought that at least 8 in 10 people with BHD have lung cysts. These lung cysts have features that are unique to BHD. For example, they are typically found at the base of the lungs and have an irregular shape. Therefore, CT scans may be useful in diagnosing BHD. The authors also discussed whether CT scans should be performed on everyone who experiences a PSP to aid the diagnosis of BHD.

A questionnaire was sent to 475 people who had a PSP between 2004 and 2017 at the Rijnstate Hospital in Arnhem, the Netherlands. 178 people completed and returned the questionnaire. Of these, 88 were included in the study for genetic testing. 3 people were found to have a mutation in FLCN. 2 of these people were related and had multiple family members with a history of collapsed lungs. The other person had a family history of kidney cancer. All 3 people had fibrofolliculomas. One person was found to have kidney cancer. This was successfully treated with surgery.

A chest CT scan was available for 83 out of 88 people. Cysts were found in 14 people, of whom 6 had multiple cysts. All 3 people with BHD had multiple lung cysts. Most of these were found in the base of the lungs, typical of BHD.

 In retrospect, all 3 people who were diagnosed with BHD in this study had features that could have allowed them to be diagnosed earlier. This highlights the importance of raising awareness of BHD among doctors who would see someone with a PSP including lung doctors, radiologists and emergency doctors. For this purpose, the BHD Foundation has created a BHD awareness leaflet.

Based on this study and other previous studies done, the authors recommend that a CT scan should be performed for everyone who presents with a PSP. They also suggest that if lung cysts are present, genetic testing for BHD should be done. A lung collapse is often an early symptom of BHD and so this would hopefully result in an earlier diagnosis of BHD. It would also allow their family members to be tested. Additionally, performing a CT scan in everyone that has a PSP could allow the diagnosis of other cystic lung diseases such as LAM.

In the future, we would like to see more studies like this being done on larger groups of people. The more people involved in research in BHD, the more confidence you can have in the data. Better quality data will help us better inform guidelines on the diagnosis and management of BHD. We launched the BHD syndrome International Registry (BIRT) to help us collect as much information about BHD as possible and drive forward research.