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Neurofibromatosis is a genetic disorder in which many soft, fleshy growths of nerve tissue (neurofibromas) grow under the skin and in other parts of the body.
Neurofibromas are flesh-colored growths of Schwann cells (which form a wrapping around peripheral nerve fibers) and other cells that support peripheral nerves. Neurofibromas, which can be felt under the skin as small lumps, usually start appearing after puberty.
Types:
There are two types of neurofibromatosis:
Causes
About half the people with neurofibromatosis inherit it. Only one gene for neurofibromatosis—from one parent—is required for the disorder to develop, and each child of an affected parent has a 50% chance of inheriting the disorder. The genes for both types have been identified. In the rest of the people, neurofibromatosis results from a spontaneous gene mutation. Thus, these people have no family history of the disorder.
Symptoms
Type 1:
About one third of people notice no symptoms, and the disorder is first suspected during a routine examination when doctors find lumps under the skin near nerves. Another third of people notice skin spots or bumps, and the remaining people notice neurologic symptoms such as weakness. In more than 90%, medium-brown (café au lait) spots develop on the skin of the chest, back, pelvis, and creases of the elbows and knees. These spots typically exist at birth or appear during infancy. Between ages 10 and 15, flesh-colored growths (neurofibromas) of varying sizes and shapes begin appearing on the skin. There may be fewer than 10 of these growths or thousands of them. Rarely, neurofibromas under the skin or an overgrowth of the bone under the neurofibroma causes structural abnormalities, such as an abnormally curved spine (kyphoscoliosis), rib deformities, enlarged long bones in the arms and legs, and bone defects of the skull. If the bone surrounding the eyeball is affected, the eyes bulge.
Neurofibromas may affect any nerve in the body but frequently grow on spinal nerve roots (the parts of the spinal nerve that emerge from the spinal cord through the spine). There, they often cause few or no problems. However, if they put pressure on (compress) the spinal cord, they can cause paralysis or disturbances in sensation in different parts of the body, depending on which part of the spinal cord is compressed. If neurofibromas compress peripheral nerves, the nerves may not function normally, and pain or weakness may result. Neurofibromas that affect nerves in the head can cause blindness, dizziness, deafness, noise in the ears (tinnitus), and incoordination.
Neurofibromatosis usually progresses slowly. As the number of neurofibromas increases, more neurologic problems may develop.
Type 2:
Auditory nerve tumors develop on both sides of the body. The tumors may cause hearing loss and sometimes dizziness, as early as age 20. People may also have other types of tumors, including gliomas and meningiomas (see Tumors of the Nervous System: Tumors That Originate in or Near the Brain ), and some develop cataracts prematurely.
Diagnosis
Doctors base the diagnosis on findings during examination. They usually do computed tomography (CT) or magnetic resonance imaging (MRI) to check for growths in the head and near the spinal cord in people who have neurologic symptoms.
Genetic testing is not yet readily available.
Treatment
No known treatment can stop the progression of neurofibromatosis or cure it. Individual neurofibromas can usually be removed surgically or shrunk with radiation therapy. When they have grown close to a nerve, surgical removal often requires removing the nerve as well.
Because neurofibromatosis can be hereditary, genetic counseling is recommended when people with this disorder are considering having children. For people who have a child with the disorder but do not have the disorder themselves, the risk of having another child with the disorder is very small.
Last full review/revision February 2009 by Margaret C. McBride, MD
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