Neurofibromatosis
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 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. There are two types of neurofibromatosis: peripheral (type 1--also known as von Recklinghausen's disease) and central (type 2). Type 1 affects about 1 of 3,000 people, and type 2 affects about 1 of 40,000.
About half of 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. In the other half of the people with neurofibromatosis, it results from a spontaneous gene mutation. Thus, neurofibromatosis can occur in people who have no family history of the disorder.
Symptoms and Diagnosis
About one third of people with peripheral neurofibromatosis notice no symptoms, and the disorder is first diagnosed during a routine examination when doctors find lumps under the skin near nerves. Another third of the people seek help for a cosmetic problem caused by the disorder, leading to its diagnosis. In the remaining third, the disorder is diagnosed when people notice neurologic problems, such as weakness due to compression of the spinal cord or nerves.
Typically, medium-brown skin spots (café au lait spots) develop on the chest, back, pelvis, elbows, and knees. These spots may 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. In some people, neurofibromas under the skin or an overgrowth of the bone under the neurofibroma produces 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, including the part surrounding the eyeball (which results in bulging eyes).
Neurofibromas may affect any nerve in the body but frequently grow on spinal nerve roots. There, they often cause few or no problems. However, if they compress the spinal cord, they can become serious, causing paralysis or disturbances in sensation in different parts of the body, depending on what 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. As the number of neurofibromas increases, more neurologic problems develop.
People who have central neurofibromatosis develop tumors in the auditory nerves (auditory tumors, or acoustic neuromas) on both sides of the body. The tumors may cause hearing loss and sometimes dizziness, as early as age 20. People who have this disorder also may have gliomas or meningiomas (see Section 6, Chapter 88), and some develop cataracts prematurely. Because this disorder can be inherited, family members may also be affected.
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.
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