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Neurofibromatoses (NF) are genetic disorders of the nervous system that cause tumors to grow on nerves. These tumors are benign, which means they are not cancer. NF also can cause abnormalities of skin and bone. The severity of symptoms varies greatly.

There are three main forms of NF:

1. NF1, formerly called peripheral neurofibromatosis or von Recklinghausen’s disease
2. NF2, formerly called bilateral acoustic neurofibromatosis, central neurofibromatosis or vestibular schwannoma
3. Schwannomatosis, until recently considered a form of NF 2

How common is NF?
About 100,000 individuals in the United States have a NF (1). NF1 is most common. It affects about 1 in 3,000 births in the United States (1, 2).

NF2 is less common, affecting about 1 in 25,000 births (1, 3). Schwannomatosis affects about 1 in 40,000 births (4). All forms of NF are found in every racial and ethnic group throughout the world and affect both sexes equally.

What causes NF?
The three forms of NF are caused by abnormalities in three different genes. The gene for NF1 is located on chromosome 17. The genes for NF2 and schwannomatosis are located on chromosome 22.

NF1 and NF2 are inherited in the same way. In about 50 percent of cases, a child inherits the abnormal gene from one parent who has the disorder. In some cases, the affected parent may have such mild symptoms that he may not know he has the disorder. The remaining half of NF1 and NF2 cases are caused by new mutations (changes) in the genes (1). This means that NF1 or NF2 can occur in a person who has no family history of the condition. The abnormal gene in NF1 and NF2 is autosomal dominant, which means that any child of only one parent with NF has a 50-50 chance of inheriting the NF gene.

Less is known about how schwannomatosis is inherited. It appears that most cases (about 85 percent) are caused by new mutations (1, 5).

What are the signs of NF1?
According to the National Institutes of Health (NIH), there are seven common signs of NF1 (1). NF1 is diagnosed in individuals who have two or more of these signs:

1. Six or more tan spots on the skin, called café-au-lait spots, that are wider than 1/5 inch before puberty or 3/5 inch after puberty. Café-au-lait means “coffee with milk” in French. These spots usually are present at birth or appear by age 2. Café-au-lait spots may increase in size and number and darken with age.
2. Freckles that appear under the arms or in the groin, usually by 7 years of age.
3. Two or more benign tumors under the skin. These are called neurofibromas. Neurofibromas grow on nerves. They usually develop at around the time of puberty, but they may develop at any age. An affected person may have any number of neurofibromas. A person also may have a single neurofibroma without having NF.
4. A tumor on the optic (eye) nerve. This kind of tumor is called an optic glioma. It rarely causes vision problems. Most of these tumors, which are usually diagnosed by 7 years of age, cause no symptoms and require no treatment.
5. Two or more tiny tan or brown Lisch nodules. These are small clumps of pigment that appear in the iris (colored part of the eye). These usually appear at around puberty and cause no vision problems.
6. A variety of bone defects, such as bowing of the legs below the knee. These usually are present at birth or develop during the first year of life.
7. A family history of NF1 in a parent, sibling or child..

How is NF1 diagnosed?
NF1 is diagnosed by physical examination. A health care provider may use a special lamp to check the skin so that he can see very light-colored café-au-lait spots. The provider may recommend tests, including X-rays, computerized tomography (CT scans) and magnetic resonance imaging (MRI). In some cases, genetic testing of a blood sample is needed to confirm the diagnosis. Some children under 8 years of age may have café-au-lait spots but no other signs of NF1. These children should be monitored carefully to see if other signs of the disorder
How does NF1 affect a person?

In many cases of NF1, symptoms are mild, and affected individuals live a normal life. Some signs of NF1, including café-au-lait spots, freckling and Lisch nodules, pose no risk to health. Other common characteristics, including short stature and large head size, also have little effect on health.

Some health problems that affect individuals with NF1 include:

• Skin neurofibromas: Some individuals have many of these benign tumors on the face and body. These tumors generally are harmless, but an affected person may have trouble dealing with the way they look on the body.
• Plexiform neurofibromas: These are deep neurofibromas that can grow inside the body and can affect many organ systems. These tumors affect about 30 percent of individuals with NF1 (6). Some plexiform neurofibromas cause no symptoms, but others can cause serious problems, depending on the organ system involved.
• Learning disabilities: Up to 65 percent of children with NF1 have learning disabilities (6). These include hyperactivity and attention and language problems (1, 6).
  Scoliosis: Up to 25 percent of children with NF1 have scoliosis, which is progressive curvature of the spine. Scoliosis can begin at an early age (6).
• Cardiovascular abnormalities: Individuals with NF1 have an increased risk of congenital heart defects, constricted or damaged blood vessels and high blood pressure (1, 6). In children, blood vessel abnormalities in the brain can sometimes cause headaches, seizures and weakness (6).
• Bulging of the eye or vision problems: These problems affect a few individuals with optic glioma.
• Cancer: In about 3 to 5 percent of affected people, one or more fibromas become malignant and require treatment with surgery, chemotherapy or radiation (1). Individuals with NF1 also appear to be at an increased risk of leukemia and certain rare cancers (2).

How is NF1 treated?
There is no cure for NF1, but there are ways to treat some of its effects. Painful or disfiguring skin tumors can be removed with surgery. However, they often grow back. Optic gliomas that affect vision can be treated with surgery and/or chemotherapy (6). Scoliosis may be treated by surgery or by wearing a brace. Bowed legs also may be treated by wearing a brace.

A number of multidisciplinary NF clinics throughout the United States address specific medical concerns and routine NF-related health care issues.

Researchers are developing drugs that target the underlying cellular defects in NF1, in order to help prevent or shrink nerve cell tumors. In the future, these new drugs may improve the treatment of NF1.

What are the signs of NF2?
Signs of NF2 include:

• Vestibular schwannomas: These are benign tumors that grow on a nerve (called the 8th cranial nerve) that goes from the ear to the brain. These tumors are called schwannomas because they come from Schwann cells, which support and protect nerve cells. They often cause pressure on the acoustic (hearing) nerves, resulting in hearing loss. Almost all individuals with NF2 develop these tumors by age 30 (3).
• Brain and spinal cord tumors: Many persons with NF2 develop benign tumors along nerve tissues elsewhere in the body, including the brain and spinal cord.
• Cataracts: Many affected individuals develop a special type of cataract early in life. A cataract is a kind of film or cloud that covers the eye’s lens. They also may develop changes in the retina, which is the light-sensing tissue that lines the back of the eye.
• Skin tumors: Persons with NF2 may have a small number of skin tumors (schwannomas). However, they have few or no café-au-lait spots or neurofibromas.

How is NF2 diagnosed?
As with NF1, NF2 usually is diagnosed by physical examination. The provider may recommend a number of imaging tests, including MRI, to look at the brain and spinal cord. MRI can detect tiny tumors, allowing for early diagnosis. In some cases, genetic testing is done to help confirm the diagnosis.

When NF2 is diagnosed, hearing tests called audiometry and brainstem auditory evoked response test are recommended. These tests help determine how well the 8th cranial nerve is working. The individual should be examined by an ophthalmologist (eye specialist) to look for cataracts and other eye problems that can contribute to vision loss.

How does NF2 affect a person?
Symptoms of NF2 usually appear in the teens or early twenties. Symptoms vary greatly in severity and can include (3, 5):

• Hearing loss
• Ringing in the ears
• Dizziness
• Facial numbness
• Balance problems
• Headaches
• Vision loss
• Numbness or weakness in parts of the body, such as the legs

How is NF2 treated?
As is the case in NF1, there is no cure for NF2, but surgery can help control symptoms. However, surgery on the 8th cranial nerve can sometimes cause additional hearing loss, so individuals and families must carefully weigh the risks and benefits of surgery. MRI scans can detect very small tumors, sometimes allowing for early treatment.

Several medical centers are examining the effectiveness of stereotactic radiosurgery in treating vestibular schwannomas associated with NF2 (7). In this treatment, a high dose of radiation is delivered precisely to the tumor without exposing the surrounding tissue to significant radiation. It is not yet known whether this treatment increases the risk of cancer.

A small, preliminary study found that a cancer drug called bevacizumab (Avastin) shrank vestibular schwannomas and improved hearing in some, but not all, individuals. However, more studies are needed on the safety and effectiveness of this treatment (8).

Spinal cord tumors also can be removed surgically, when necessary. However, many of these tumors grow slowly and produce few or no symptoms. In such cases, the health care provider monitors the tumors with imaging tests.

When is NF1 or NF2 testing recommended for couples planning pregnancy?
Some women and men planning pregnancy may not know that they have NF1 or NF2. They may have very mild symptoms that have gone undiagnosed, or they may not have developed symptoms. In such cases, a family health history done during a preconception or early prenatal visit can help identify couples at increased risk of having a baby with NF. The health care provider may suggest testing for NF1 or NF2 if an individual:

• Has a child with possible signs of NF
• Has a family history of NF in a parent, sibling or child
• Has a personal or family history of NF-related conditions, such as skin tumors, freckling (in a NF1-related pattern) or hearing loss

If a woman or her partner is found to have NF1 or NF2, they should consider consulting a genetic counselor. Genetic counselors can help a family understand the chances of a birth defect occurring in a pregnancy and can discuss the possibility of prenatal testing. Genetic counseling is available at most large medical centers and teaching hospitals. To find a genetic counselor in their area, individuals can ask their health care provider or contact the National Society of Genetic Counselors.

What are the signs and symptoms of schwannomatosis?
Affected individuals develop schwannomas, as do many people with NF2. However, the schwannomas do not develop on the 8th cranial nerves, so affected individuals do not develop hearing loss. The main symptom of schwannomatosis is pain, which can occur in any part of the body (3). Affected individuals also may have other neurological problems, such as numbness, tingling or weakness in fingers and toes.

How is schwannomatosis diagnosed?
As with NF1 and NF2, schwannomatosis is diagnosed with a physical examination. Imaging tests, such as MRI, often are used to rule out vestibular schwannomas and NF2.

How is schwannomatosis treated?
Schwannomas often can be surgically removed to relieve pain, though tumors sometimes grow back. Affected individuals also can be treated with pain medications.

Do neurofibromatoses affect pregnancy?
Most women with NF1 have healthy pregnancies. However, neurofibromas may increase in size and number during pregnancy, apparently because of hormonal changes. This sometimes may contribute to pregnancy complications, such as compression of the umbilical cord or obstruction of the birth canal (requiring cesarean section) (2). Pregnant women with NF1 also may be at increased risk of high blood pressure (2). A pregnant woman with NF1 should be cared for by an obstetrician who is familiar with NF1, in close consultation with her NF specialist.

There is little information on the effects of NF2 or schwannomatosis on pregnancy. Women with NF2 and spinal tumors may need imaging tests before labor and birth to make sure it’s safe for them to have epidural anesthesia (3).

Is genetic testing available to help diagnose neurofibromatosis?
Yes, for NF1 and NF2. Though NF1 and NF2 usually are diagnosed with a physical examination, providers sometimes use genetic testing to help confirm the diagnosis. Genetic testing can be conducted before birth to help identify individuals who don’t show symptoms but have a family history of these disorders. However, genetic tests cannot predict the degree of severity of either form of NF. There is no definitive genetic test available now for schwannomatosis.

Does the March of Dimes conduct research on NF?
The March of Dimes has funded NF studies, including basic research on the causes of these and other nervous system diseases. For example, researchers are studying genetically controlled events in the embryo that are crucial to development of the body’s nervous system and factors that regulate growth and maintenance of nerves. One grantee is seeking to determine how mutations in the NF1 gene cause bone abnormalities such as scoliosis, in order to develop drugs to help prevent them.


Where can I get further information about NF?

• The National Institute of Neurological Disorders and Stroke (NINDS)
• The Children’s Tumor Foundation
• Neurofibromatosis, Inc.

References

1. National Institutes of Neurological Disorders and Stroke (NINDS). (2009). Neurofibromatosis fact sheet.
2. Friedman, J.M. (2009). Neurofibromatosis 1. Gene Reviews. University of Washington at Seattle.
3. Evans, D.G. (2009). Neurofibromatosis 2. Gene Reviews. University of Washington at Seattle.
4. Children’s Tumor Foundation. (2009). Living with NF: Schwannomatosis.
5. Lu-Emerson, C. & Plotkin, S.R. (2009). The neurofibromatoses. Part 2: NF2 and schwannomatosis. Reviews in Neurological Diseases, 6 (3), E81-E86.
6. Williams, V.C., Lucas, J., Babcock, M.A., Gutmann, D.H., Korf, B. & Maria, B.L. (2009). Neurofibromatosis type 1 revisited. Pediatrics, 123 (1), 123-133.
7. Asthagiri, A.K., Parry, D.M., Butman, J.A., Kim, H.J., Tsilou, E.T., et al. (2009). Neurofibromatosis type 2. Lancet, 373, 1974-1986.
8. Plotkin, S.R., Stemmer-Rachamimov, A.O., Barker, F.G., Halpin, C., Padera, T.P., et al. (2009). Hearing improvement after bevacizumab in patients with neurofibromatosis type 2. New England Journal of Medicine, 361 (4), 358-367.

May 2010