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What is Neurofibromatosis?


2008-02-28

Neurofibromatosis

The neurofibromatoses are genetic disorders of the nervous system that primarily affect the development and growth of neural (nerve) cell tissues. These disorders cause tumors to grow on nerves and produce other abnormalities such as skin changes and bone deformities.

Although many affected persons inherit the disorder, between 30 and 50 percent of new cases arise spontaneously through mutation (change) in an individual's genes.

Neurofibromatosis was discovered in 1882 by von Recklinghausen. Joseph Merrick, the Elephant Man, was once considered to have been afflicted with either elephantiasis or neurofibromatosis type I. However, it is now generally believed that Merrick suffered from the very rare Proteus syndrome or perhaps a combination of the two conditions.

Early stages of Neurofibromatosis The neurofibromatoses are a group of three genetically distinct but related disorders of the nervous system that cause tumors to grow around the nerves. Tumors begin in the cells that make up the myelin sheath, a thin membrane that envelops and protects nerve fibers, and often spread into adjacent areas. The type of tumor that develops depends on its location in the body and the kind of cells involved. The most common tumors are neurofibromas, which develop in the tissue surrounding peripheral nerves. Most tumors are non-cancerous, although occasionally they become cancerous over time.

An estimated 100,000 Americans have a neurofibromatosis (the singular form of neurofibromatoses) disorder, which occurs in both sexes and in all races and ethnic groups. Scientists have classified the disorders as neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and a type that was once considered to be a variation of NF2 but is now called schwannomatosis.

NF1 - A progressive disorder, which means most symptoms will worsen over time, although a small number of people may have symptoms that stay the same and never get any worse. It isn't possible to predict the course of any individual's disorder. In general, most people with NF1 will develop mild to moderate symptoms, and if complications arise they will not be life-threatening. Most people with NF1 have a normal life expectancy.

NF2 - This rare disorder affects about 1 in 40,000 people and is characterized by slow-growing tumors on the eighth cranial nerve. This nerve has two branches: the acoustic branch helps people hear by transmitting sound sensations to the brain; the vestibular branch helps people maintain their balance. The tumors of NF2, called vestibular schwannomas, press against and sometimes even damage the nerves they surround. In some cases they will also damage nearby vital structures such as other cranial nerves and the brainstem, leading to a potentially life-threatening situation. Individuals with NF2 are at risk for developing other types of nervous system tumors such as spinal schwannomas, which grow within the spinal cord and between the vertebrae, and meningiomas, which are tumors that grow along the membranes covering the brain and spinal cord.

Schwannomatosis - A newly recognized neurofibromatosis that is genetically and clinically distinct from NF1 and NF2. Like NF2 it occurs rarely. Inherited forms of the disorder account for only 15 percent of all cases. Researchers still don't fully understand what causes the tumors and the intense pain that are characteristics of the disorder.

The first noticeable sign of neurofibromatosis is usually the presence of multiple cafe-au-lait spots. If your child has several of these spots, ask your doctor to do a thorough examination; he or she may need to screen your child for other signs of NF.

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