Neurofibromatosis, type 1 (NF1)

Neurofibromatosis, type 1 (NF1) is a genetic condition that can cause certain pigment (color) changes on the skin, an increased risk for certain types of cancer, and benign tumors in the skin, brain, and other parts of the body. The signs of NF1 can usually be found in childhood, and the first signs that are found are often the skin pigment changes, which can sometimes be very subtle. As people with NF1 get older, their chance to develop the tumors and cancer increase.

Mutations (or changes) in the NF1 gene causes NF1, and are inherited in an autosomal dominant pattern, meaning that children of a mutation carrier each have a 50% risk to inherit the mutation and associated cancer risks. Notably, women and men both have the NF1 genes and have the same chances to inherit and pass down mutations in these genes. Therefore, both sides of the family are important when assessing inherited risk. About 50% (or 1 in 2 people) with NF1 will also have a parent with NF1. The other 50% have no family history and will be the first ones in their family with this condition.

NF1 is suspected in a person with any of the following:

  • Six or more cafe-au-lait (light brown spots)
  • Two or more neurofibromas (a type of benign nerve tumor), or one plexiform neurofibroma (a more specific type of neurofibroma); neurofibromas can range from small, discrete lumps to larger internal masses
  • Freckles in the groin or underarm area
  • Optic glioma (benign tumors on the nerve that connects the eyes to the brain, which can sometimes affect vision)
  • Two or more Lisch nodules (benign growths, like freckles, on the iris of the eye)
  • A first-degree relative (parent, sibling, or child) with NF1

Individuals with NF1 are also at an increased risk to have scoliosis (curvature of the spine) or other bone abnormalities, as well as other tumors of the gastrointestinal tract or central nervous system. About half of people with NF1 also have learning disabilities.

If you or your family meet any of the above criteria, a meeting with a pediatric or adult genetics specialist can be helpful to further determine if someone has NF1.

NF1 and cancer

The overall lifetime risk for cancer in NF1 is approximately 60%, which includes an increased risk for breast cancer, and certain gastrointestinal and central nervous system cancers. Studies have shown that women with NF1 have an elevated risk to develop breast cancer before the age of 50. After age 50, the risk to develop breast cancer returns to the level of other women in the general population.

Diagnosing NF1

NF1 is diagnosed by detailed physical examination (usually done by a geneticist) and family history. The geneticist can look for the signs of NF1 during the examination and usually can determine if someone has NF1 or not based on that physical exam.

Genetic Testing for NF1

Genetic testing for NF1 is not always needed, as it can be diagnosed via physical exam by a genetics specialist. There are some instances where genetic testing can be helpful:

  • If someone is suspected to have NF1 but this is not confirmed by the physical exam
  • If a child has a suspicious tumor, and genetic testing would immediately impact their treatment
  • If a parent who has NF1 would like to to do prenatal or preconception testing to determine if an embryo or pregnancy is also affected with NF1

If genetic testing is being done, there are a couple of different approaches:

  • Single site analysis: Testing specific to a known mutation in the family
  • Full gene sequencing and rearrangement analysis: Comprehensive testing to search for all currently detectable mutations in the genes.
  • Gene panels: Newer, more broadly based gene tests that would include not only the NF1 genes, but other genes known or suspected to be associated with the signs of NF1 or breast cancer. For example, mutations in the SPRED1 gene can result in skin findings that can be similar to NF1, but does not have the increased risk for tumors and cancer that individuals with NF1 have. The NF1 gene is also on some panels that are testing for an increased risk for breast cancer, along with genes such as BRCA1 and BRCA2.

Medical Management Screening for NF1

If you (or your child) are diagnosed with NF1, it is recommended to establish care with a neurofibromatosis specialist who will evaluate and manage for any neurologic or other complications associated with this condition, including risk for NF1-associated cancers.

The National Comprehensive Cancer Network (NCCN) recommends that women who have a diagnosis of NF1 should start annual mammogram screening at age 30, and should consider annual breast MRIs between the ages of 30 and 50. It is important to note the possibility that benign neurofibromas within the breast tissue may cause false- positive results on MRI. There is not currently any data or evidence to recommend risk-reducing mastectomies for women with NF1, but it may be considered on a case-by-case basis depending on family history. More personalized recommendations will take into account your personal and family history and should be discussed with your provider.

 

Additional Resources:

The Washington University Neurofibromatosis Center

Children’s Tumor Foundation

Neurofibromatosis Network


Last updated on Sep 4th, 2018