Neurofibromatosis

Neurofibromatosis (NF), or von Recklinghausen disease, is a genetic disease in which patients develop many soft tumors (neurofibromas) under the skin andthroughout the nervous system. The tumors develop from cells called neural crest cells, which are found in developing fetuses (unborn babies). Normally, neural crest cells turn into other types of cells that form nerves; bony structures of the head and neck; and pigment cells, which provide color to body structures. But in a person with neurofibromatosis, a genetic defect causes theneural crest cells to develop abnormally, producing tumors and malformationsof the nerves, bones, and skin.

About one in every 4,000 babies born has neurofibromatosis (NF). Two types ofNF exist, NF-1 (90% of all cases), and NF-2 (10% of all cases). The chance of a person with NF passing on the genetic defect to a child is 50%. However,not all cases of NF are inherited. About half are due to a spontaneous mutation (a permanent change in the structure of a specific gene) that occurs afterbirth.

NF-1 is suspected if any two of these signs are present:

  • The presenceof café-au-lait (French for coffee-with-milk) spots. These are patchesof tan or light brown skin, usually about 5-15 mm in diameter. Nearly all patients with NF-1 have these spots.
  • Multiple freckles in the armpit orgroin.
  • Tiny tumors called Lisch nodules in the iris (colored area) of the eye.
  • Neurofibromas. These are soft, rubbery tumors that occur under the skin, along nerves or within the gastrointestinal tract. The skin over neurofibromas may be purplish.
  • Skeletal deformities, such as a twisted spine (scoliosis), curved spine (humpback), or bowed legs.
  • Tumors along the optic nerve, which cause vision problems in about 20% of patients.
  • The presence of NF-1 in a patient's parent, child, brother or sister.

Children with NF-1 are very likely to have speech problems, learning disabilities, or attention deficit disorder. They may also develop seizure disorders,or the abnormal accumulation of fluid within the brain (hydrocephalus). A number of cancers are more common in patients with NF-1.

Patients with NF-2 do not necessarily have café-au-lait spots, freckling, and neurofibromas of the skin. They are more likely to have hearing loss,due to tumors along the acoustic nerve. These tumors may spread to neighboring nerves, causing weakness of the muscles of the face, headache, dizziness,poor balance, and uncoordinated walking. Cloudy areas on the lens of the eye(called cataracts) frequently develop at an unusually early age. As in NF-1,the chance of brain tumors developing is unusually high.

Monitoring the progression of neurofibromatosis involves careful testing of vision and hearing. X-ray studies of the bones are frequently done to watch for the development of deformities. CT scans and MRI scans are performed to track the development and progression of tumors in the brain and along the nerves.

There are no available treatments for the genetic disorders that underlie neurofibromatosis, but some of the symptoms can be treated. Skin tumors can be surgically removed. Some brain tumors and tumors along the nerves, can be surgically removed or treated with drugs (chemotherapy) or x-ray treatments (radiation therapy). Twisting or curving of the spine and bowed legs may require surgical treatment, or the wearing of a special brace.

The outlook for a person with NF depends on the type of tumors that develop.As tumors grow, they begin to destroy surrounding nerves and structures. Thiscan cause blindness, deafness and problems with balance and coordination, making it difficult to walk. Deformities of the bones and spine can also interfere with walking and movement.

There is no known way to prevent NF cases which occur due to a spontaneous change in the genes (mutation). New cases of inherited NF can be prevented withcareful genetic counseling. A person with NF can be made to understand thateach of his or her offspring has a 50% chance of also having NF. When a parent has NF, and the specific genetic defect causing the parent's disease has been identified, tests can be performed on the fetus (developing baby) during pregnancy. The tissue can then be examined for the presence of the parent's genetic defect. Some families use this information to prepare for the arrival of a child with a serious medical problem. Other families choose not to continue the pregnancy.

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