Getting Your BHD Diagnosis.

We know that receiving a diagnosis of BHD can be a confusing process. We spoke to Dr Derek Lim, Consultant Clinical Geneticist at Birmingham Women’s and Children’s Hospital, UK to help understand what happens at an appointment with a clinical geneticist. Although this pathway is specific to the UK, we hope this provides a general idea of what to expect when you see a clinical geneticist.

How do you get an appointment with a clinical geneticist?

Dr Lim described the three main routes by which individuals are referred to his BHD genetics clinic.

1. Individuals who have already had a positive diagnostic genetic test for BHD and are referred to discuss the diagnosis, management, surveillance and genetic counselling.
2. Individuals who are referred to him for a possible diagnosis of BHD (i.e. they have not yet had a genetic test).
3. Individuals who have a family member who has been diagnosed with BHD.

What happens during your appointment?

What happens during the appointment will depend on whether an individual has already had a genetic test for BHD.

 If this is the case (i.e. route number 1), then the genetic test result is explained to them along with an explanation of BHD. This includes the different symptoms of BHD and recommended management and surveillance strategies. Dr Lim explained he would also take a family history, examine individuals for skin bumps, refer them for a CT scan of their lungs and arrange a scan of the kidneys.

If an individual has not had a genetic test for FLCN and is being referred for a possible BHD diagnosis (i.e. route number 2), then Dr Lim explains what BHD is and offers a skin examination to check for skin bumps. If there is evidence of BHD, a genetic test to look for FLCN variants will be offered. In this instance, the results are often relayed in a letter. A follow-up consultation can be arranged if required.

If an individual has been referred to the clinic because a family member has been diagnosed with BHD (i.e. route number 3), a genetic test for the specific variant found in the family will be offered. Sometimes it may be appropriate to test another family member first (e.g. a parent who is also being seen in the clinic).

 Why is it important to know the specific FLCN variants?

There are several reasons why knowing the specific variant an affected individual has is important. Firstly, from a clinical perspective, the test required for other family members is simpler and cheaper than having to test for variants in the entire FLCN gene. Dr Lim likened this to finding a spelling mistake in a book. It is a much easier task to find the spelling mistake once you have been able to narrow down the page, paragraph and line the spelling mistake is in. Secondly, knowing the specific variant is also useful to predict the effect of the mutation on the function of the FLCN protein. In turn, this allows the prediction of whether the FLCN variant will be pathogenic.  In other words, how likely it is to lead to any symptoms of BHD? Finally, it is useful for scientists to know what different variants exist so that research can be done to find if there are any links between genotype (the genetic code) and phenotype (the symptoms of BHD), e.g. whether having a particular FLCN variant increases the risk of developing kidney cancer.

What are some of the common questions asked during an appointment?

During appointments a lot of information can be given in a short space of time. It may be difficult to think of questions that might be relevant.  We asked Dr Lim the most common questions he is asked in his clinic and here are his top 3:

1. When should my children be tested?
   In the UK, monitoring of the kidneys (preferably a MRI scan) begins at 18 years of age and so appointments to discuss genetic testing are usually made between the ages of 16 and 18.
2. How often do I need lung scans?
   In the UK, regular monitoring of the lungs isn’t recommended due to repeated radiation exposure through CT imaging. A CT scan is recommended at diagnosis if the individual has not already had one. Importantly, individuals are made aware of the symptoms of a pneumothorax and what to do if an individual experiences one.
3. Will I get skin bumps and what are the available treatments?
   Although skin bumps are the most common manifestation of BHD, it is not guaranteed an individual will develop them Some individuals may only have a few whereas others may have hundreds. There are treatments available. However, they do not prevent the formation of new skin bumps. You can find a list of possible treatments here.

We are thankful to Dr Lim for providing us with his insight into what happens during a clinical genetics appointment. If you have any questions about genetic testing for BHD please get in touch with us. We will be happy to help.

• Published October 2023
• Due for review January 2025