Neurofibromatosis type 1

What causes neurofibromatosis type 1?

Neurofibromatosis type 1 is caused by changes (mutations) in the NF1 gene. NF1 is a tumor suppressor gene, which means that it encodes a protein that stops cells from growing and dividing too rapidly or in an uncontrolled way. Mutations in NF1 result in an abnormal protein that is unable to carry out its normal role. This contributes to the development of the many different types of tumors found in neurofibromatosis type 1.

People with neurofibromatosis type 1 are typically born with one mutated copy of the NF1 gene in each cell and are, therefore, genetically predisposed to develop the tumors associated with the genetic disorder. For a tumor to form, two copies of the NF1 gene must be mutated. The mutation in the second copy of the NF1 gene is considered a somatic mutation because it occurs during a person's lifetime and is not inherited. Almost everyone who is born with one NF1 mutation acquires a second mutation in many cells and develops the tumors characteristic of neurofibromatosis type 1.

Last updated on 05-01-20

How is neurofibromatosis type 1 diagnosed?

The diagnosis of neurofibromatosis type 1 (NF1) is usually based on the presence of characteristic signs and symptoms. Specifically, doctors look for two or more of the following features to make a diagnosis of NF1:

  • Six or more cafe-au-lait spots (measuring more than 5 mm across in children and more than 15 mm across in adolescents and adults)
  • Two or more neurofibromas of any type or one plexiform neurofibroma (a neurofibroma that involves many nerves)
  • Freckling in the underarm and/or groin
  • Optic glioma
  • Two or more Lisch nodules (clumps of pigment in the colored part of the eye that do not interfere with vision)
  • Bone abnormalities including sphenoid dysplasia (absence of bone surrounding the eye) or tibial pseudarthrosis (incomplete healing of a fracture)
  • A parent, sibling, or child who has been diagnosed with NF1.

Because many of the signs and symptoms associated with NF1 develop with age, it can sometimes take several years to make a diagnosis in children who do not have a family history of the condition.

Genetic testing for changes (mutations) in the NF1 gene is available, but it is often not necessary. Prenatal testing and preimplantation genetic diagnosis is only an option if the disease-causing mutation in the family is known.

Last updated on 05-01-20

How is neurofibromatosis type 1 inherited?

Neurofibromatosis type 1 (NF1) is inherited in an autosomal dominant manner. This means that a person needs a change (mutation) in only one copy of the gene associated with the disease to have a genetic predisposition to the tumors associated with NF1.
In approximately half of cases, the person with NF1 inherits the mutation from a parent with the genetic disease. Other cases may result from new ( de novo) mutations in the gene; these cases occur in people with no history of the disorder in their family. A person with NF1 has a 50% chance with each pregnancy of passing along the mutated gene to his or her child.

Last updated on 05-01-20

What is the long-term outlook for people with neurofibromatosis type 1?

The long-term outlook (prognosis) for people with neurofibromatosis type 1 (NF1) varies based on the severity of the condition and the signs and symptoms present in each person. Although people with NF1 can live relatively long and healthy lives, their life expectancy tends to be lower than in the general population.

The most common causes of death in people with NF1 are hypertension, symptoms related to spinal cord tumors, and malignancy. Fortunately, early detection and prompt attention to complications associated with NF1, including tumors and cancers can improve quality of life and survival of the condition.

Last updated on 05-01-20

How might neurofibromatosis type 1 be treated?

The treatment of neurofibromatosis type 1 (NF1) is based on the signs and symptoms present in each person. There is currently no way to prevent or stop the growth of the tumors associated with NF1.

Neurofibromas located on or just below the skin that are disfiguring or irritating may be surgically removed. Malignant (cancerous) peripheral nerve sheath tumors are generally completely removed with surgery (complete surgical excision), although some cases may also require chemotherapy. Radiation therapy is not recommended because it may increase the risk of the tumors to become malignant. Most optic gliomas associated with NF1 do not cause any symptoms and, therefore, do not require treatment; however, optic gliomas that threaten vision may be treated with surgery and/or chemotherapy. Surgery may also be recommended to correct some of the bone malformations (such as scoliosis) associated with NF1.

GeneReviews Web site offers more specific information for the treatment and management of NF1.

Last updated on 05-01-20

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Name: Neurofibromatosis Network 213 S. Wheaton Ave.
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Ana Rath and Stéphanie NGUENGANG WAKAP. Prevalence of rare diseases: Bibliographic data », Orphanet Report Series, Rare Diseases collection, January 2020, Number 2 : Diseases listed by decreasing prevalence, incidence or number of published cases Orphanet Report Series - Prevalence of rare diseases: Bibliographic data - January 2020 - Number 2. January 2020; Number 2. 64. Reference Link Orphanet Reference Link

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