Neurofibromatosis

Neurofibromatosis (noor-o-fy-bro-ma-TO-sis) is a group of genetic disorders that cause tumors to grow on nerves. It is also characterized by skin changes and bone deformities.

Neurofibromatosis type 1 is also called von Recklinghausen's disease, after the German physician Friedrich von Recklinghausen (1833–1910), who described it in 1882. The tumors that he noted, called neurofibromas (nooro-fy-BRO-mas), arise from the cells that make up the sheaths that cover the nerves.

NF-1 and NF-2 neurofibromatoses occur in both sexes and in all racial and ethnic groups, as does schwannomatosis. In the United States, NF-1 occurs in about 1 in every 3,000 to 1 in every 4,000 persons. There were about 100,000 persons with NF-1 in the United States as of 2015. NF-2 is 10 times less common, occurring in about 1 in 37,000 people per year worldwide. Schwannomatosis is even rarer than NF-2, occurring in about 1 person in every 50,000 per year worldwide.

Although many people who have neurofibromatosis inherited it from one of their parents, between 30 and 50 percent develop it spontaneously from a mutation (change) in their genes before birth.

Neurofibromatosis is inherited as an autosomal (non-sex-linked) dominant disorder, which means that each child born to a parent with neurofibromatosis has a 50 percent chance of inheriting the defective gene and developing the disease.

Genes produce proteins that determine the physical and metabolic characteristics of a person's body, everything from the color of a person's hair to how fast a person burns fat. Scientists have discovered that normal neurofibromatosis genes produce proteins that suppress tumors. This function suggests that when the genes are defective, they may fail to produce enough of these proteins, thus allowing the growth of tumors. Researchers continue to investigate whether insufficient protein contributes to the development of neurofibromatosis.

The signs and symptoms of neurofibromatosis vary greatly among individuals even in the same family. Many people do not know that they have NF-1 until it is diagnosed during a routine physical exam. The disease is usually mild.

NF-1 produces many soft, bumpy, or stalk-like tumors under the skin. Another common sign of this disorder is light-brown patches on the skin called café-au-lait spots. Although these spots may appear in people who do not have NF-1, people with NF-1 usually have six or more of them. Signs may also include learning disabilities; vision disorders; freckles in the armpits or groin areas; growths in the eye or on the optic nerve; deformed bones; and scoliosis, a side-to-side curvature of the spine.

These signs first appear in infancy or early childhood and increase as a person grows older. Occasionally, the tumors of NF-1 are massive; in rare cases, they become cancerous. They may also occur inside the body, squeezing or blocking internal organs.

The symptoms of NF-2 include tumors on the auditory (acoustic) nerves. These growths can cause loss of hearing and may damage nearby nerves and structures in the brain. Tinnitus (ti-NY-tus; a ringing in the ears), balance disturbances, or headache can occur. People with NF-2 may first notice these symptoms in their teen or early adult years.

The signs of schwannomatosis include intense, often disabling pain that results from the pressure on the nerves caused by the growth of schwannomas, which are a distinctive type of benign tumor. Schwannomas take their name from the type of cell in which they grow (Schwann cells), which are specialized cells that help protect the nerves outside the central nervous system and keep them alive. Schwannomatosis is different from NF-1 and NF-2 in that its symptoms appear most often in adults over 30 years of age. In addition, patients with schwannomatosis may have schwannomas growing in only one area of the body, such as an arm, leg, or segment of the spine.

It should be noted that the presence of significant high blood pressure in a patient with neurofibromatosis should cause the physician to search for an associated tumor of the adrenal gland called pheochromocytoma (fee-oh-croh-moh-sye-TOE-ma), which causes hypertension by the release of catecholamines * .

The diagnosis of neurofibromatosis is made mainly by noting its outward signs. Internal viewing techniques, such as MRI * (magnetic resonance imaging), are sometimes needed as well. There was no cure for any of the three forms of neurofibromatosis as of 2016. Treatment is designed to control symptoms.

Operations and braces may be needed to correct scoliosis. Surgery may also be performed to remove tumors that are exceptionally large or painful or that press on organs. Unfortunately, the tumors often grow back. Schwannomatosis can be treated in some cases by surgical removal of the schwannomas and by managing the patient's pain with strong medications.

Various cancer treatments may be used in the rare instances in which the patient's tumors become malignant * . Progress in biomedical research into the causes of neurofibromatosis has raised hopes that someday there will be an effective treatment to slow or halt the growth of the tumors.

See also Genetic Diseases: Overview • Tinnitus • Tumor

* genes (JEENS) are chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.

* catecholamines (kat-e-KOla-meens) are hormones and neurotransmitters such as epinephrine and dopamine.

* MRI (short for magnetic resonance imaging) produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.

* malignant (ma-LIG-nant) refers to a condition that is severe and progressively worsening.