Genetics of Neurofibromatosis (NF)

Genetics play an important role in all forms of neurofibromatosis (NF). Understanding the basics can help individuals and families make informed decisions about care, testing, and family planning.

This information is meant to support understanding — not to replace conversations with healthcare providers or genetic counsellors.

Why Genetics Matter in NF

The genes involved in NF help regulate how cells grow and divide.
When one of these genes does not function as expected, cells may continue dividing, which can lead to tumour growth.
Because these genes normally help prevent uncontrolled cell growth, they are often referred to as tumour suppressor genes.

Different forms of NF are associated with changes in different genes:

  • NF1 is caused by changes in the NF1 gene (chromosome 17)
  • NF2-related schwannomatosis (NF2-SWN) is caused by changes in the NF2 gene (chromosome 22)
  • Other forms of schwannomatosis are linked to SMARCB1 or LZTR1 genes (chromosome 22)

Is NF hereditary?

For NF1 and NF2-related schwannomatosis:

  • About 50% of people inherit the condition from a parent
  • The other 50% develop NF due to a spontaneous (new) genetic change
  • Both NF1 and NF2-SWN follow autosomal dominant inheritance, meaning:
  • A person with NF has a 50% chance of passing the condition to each child
  • NF does not skip generations
  • If a child does not inherit the altered gene, they do not have NF and cannot pass it on
  • Severity cannot be predicted, even within the same family. This is known as variable expressivity.

Segmental and Mosaic NF

Some people have NF due to a genetic change that occurred after conception, resulting in a mixture of cells with and without the altered gene.

Segmental NF
  • Features are usually limited to one area of the body
  • May appear as café-au-lait spots, neurofibromas, or tumours confined to a specific region
  • Occurs in NF1, NF2-SWN, and schwannomatosis
Mosaic NF
  • Features may be milder or affect multiple areas of the body
  • Can look similar to a mild form of NF
  • Importantly, individuals with segmental or mosaic NF may still have a risk of passing NF to their children, sometimes in a more generalized form.

Genetic Counselling

Genetic counselling can help individuals and families better understand the genetics of neurofibromatosis (NF), explore testing options, and talk through questions about inheritance and family planning.

In British Columbia, genetic counselling related to NF is typically accessed through the provincial medical genetics program. Referrals are usually made by a primary care provider or specialist.
Unlike some healthcare systems, genetic counselling in BC is not always immediately available, and wait times can vary depending on location, urgency, and clinical need. Access may feel limited, and everyone who seeks genetic counselling will be referred right away.

A genetic counsellor can help:

  • Explain how NF is inherited
  • Discuss whether genetic testing may be useful in your situation
  • Clarify what genetic test results can, and cannot, tell you
  • Support conversations about family planning
  • Help interpret results once testing is complete

Genetic counselling is not required for everyone with NF, and not all individuals or families choose to pursue it. For many people, a clinical diagnosis and regular medical follow-up provide sufficient guidance. If genetic counselling is not immediately available, individuals may still receive care and monitoring through their primary care provider and relevant specialists.

Some people choose to seek private genetic counselling, which may offer shorter wait times but can involve out-of-pocket costs. This is a personal decision and not necessary for most people.

If you’re unsure whether genetic counselling is appropriate for you or how to access it in BC, we can help you think through options and prepare questions for your healthcare provider.

Genetic Testing

Genetic testing for NF is available but optional.

In British Columbia genetic testing is typically accessed through the Provincial Medical Genetics Program, with a referral from a primary care provider or specialist. NF, especially NF1, can often be diagnosed clinically, based on established diagnostic criteria, without genetic testing.

Reasons people choose genetic testing may include:
  • Confirming a diagnosis
  • Supporting diagnosis in young children
  • Clarifying inheritance for family members
  • Considering reproductive options
Important things to know:
  • Genetic testing cannot predict severity or future complications
  • Publicly funded testing is not a rapid service and wait times vary
  • Some people choose private testing for faster results, which may involve out-of-pocket costs
Results may include:
  • A pathogenic variant (confirming NF)
  • No variant detected (which does not always rule out NF)
  • A variant of uncertain significance (VUS)

A genetics counsellor can help interpret results and next steps.

Genetics Explainer Video

Questions to Ask Your Healthcare Provider

  • If you’re considering genetic testing or learning more about the genetics of NF, these questions may help guide your conversation:
  • Do my symptoms meet the clinical criteria for NF, or would genetic testing be helpful?
  • What are the benefits and limitations of genetic testing in my situation?
  • How is genetic testing accessed in British Columbia?
    What are the expected wait times for testing?
    What would the possible results mean for my care or my family?
  • Are there reasons I might choose not to pursue genetic testing right now?

A Supportive Note

Decisions about genetics and testing are personal. There is no single “right” path only the path that feels most appropriate for you and your family. If you’re unsure where to start, we can help you think through questions to discuss with your healthcare provider.

Genetics can raise complex medical and emotional questions. You don’t have to navigate them alone. The Tumour Foundation is here to help you understand your options, prepare for conversations, and feel supported at every step of the journey.

If helpful, we can support you in preparing for these conversations or help clarify next steps.