Neurofibromatosis

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Overview

Neurofibromatoses are a group of genetic disorders that cause tumors to form on nerve tissue. These tumors can develop anywhere in the nervous system, including the brain, spinal cord and nerves. There are three types of neurofibromatosis: neurofibromatosis 1 (NF1), neurofibromatosis 2 (NF2) and schwannomatosis.

Symptoms

Flat, light brown spots on the skin (cafe au lait spots). ...

Freckling in the armpits or groin area. ...

Tiny bumps on the iris of the eye (Lisch nodules). ...

Soft, pea-sized bumps on or under the skin (neurofibromas). ...

Bone deformities. ...

Tumor on the optic nerve (optic glioma). ...

Learning disabilities.

Causes

Neurofibromatosis is caused by genetic defects (mutations) that either are passed on by a parent or occur spontaneously at conception. The specific genes involved depend on the type of neurofibromatosis:

NF1. The NF1 gene is located on chromosome 17. This gene produces a protein called neurofibromin that helps regulate cell growth. The mutated gene causes a loss of neurofibromin, which allows cells to grow uncontrolled.

NF2. The NF2 gene is located on chromosome 22, and produces a protein called merlin (also called schwannomin), which suppresses tumors. The mutated gene causes a loss of merlin, leading to uncontrolled cell growth.

Schwannomatosis. So far, two genes are known to cause schwannomatosis. Mutations of the genes SMARCB1 and LZTR1, which suppress tumors, are associated with this type of neurofibromatosis.

Risk factors

The biggest risk factor for neurofibromatosis is a family history of the disorder. About half of people who have NF1 and NF2 inherited the disease from an affected parent. People who have NF1 and NF2 and whose relatives aren't affected are likely to have a new gene mutation.

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Complications

Complications of neurofibromatosis vary, even within the same family. Generally, complications result from tumors that affect nerve tissue or press on internal organs.

NF1 complications

Complications of NF1 include:

Neurological problems. Learning and thinking difficulties are the most common neurological problems associated with NF1. Uncommon complications include epilepsy and the buildup of excess fluid in the brain.

Concerns with appearance. Visible signs of neurofibromatosis — such as extensive cafe au lait spots, many neurofibromas in the facial area or large neurofibromas — can cause anxiety and emotional distress, even if they're not medically serious.

Skeletal problems. Some children have abnormally formed bones, which can result in bowing of the legs and fractures that sometimes don't heal. NF1 can cause curvature of the spine (scoliosis) that may need bracing or surgery. NF1 is also associated with decreased bone mineral density, which increases the risk of weak bones (osteoporosis).

Vision problems. Sometimes a tumor develops on the optic nerve (optic glioma), which can affect vision.

Problems during times of hormonal change. Hormonal changes associated with puberty or pregnancy might cause an increase in neurofibromas. Most women who have NF1 have healthy pregnancies but will likely need monitoring by an obstetrician who is familiar with the disorder.

Cardiovascular problems. People who have NF1 have an increased risk of high blood pressure and may develop blood vessel abnormalities.

Breathing problems. Rarely, plexiform neurofibromas can put pressure on the airway.

Cancer. An estimated 3% to 5% of people who have NF1 develop cancerous tumors. These usually arise from neurofibromas under the skin or from plexiform neurofibromas. People who have NF1 also have a higher risk of other forms of cancer, such as breast cancer, leukemia, colorectal cancer, brain tumors and some types of soft tissue cancer. Women who have NF1 should start screening for breast cancer at an earlier age than the general population.

Benign adrenal gland tumor (pheochromocytoma). This noncancerous tumor secretes hormones that raise your blood pressure. Surgery is usually needed to remove the pheochromocytoma.

NF2 complications

Complications of NF2 include:

Partial or total deafness

Facial nerve damage

Vision problems

Small benign skin tumors (skin schwannomas)

Weakness or numbness in the extremities

Multiple benign brain tumors or spinal tumors (meningiomas) requiring frequent surgeries


Prevention

While there is no treatment that can reverse NF1, its signs and symptoms can be addressed. Tumors, in particular, may warrant chemotherapy, radiation, surgery or a combination of treatments. In about 60% of people with NF1, symptoms are mild and can be monitored without the need for treatment.