There are two types of neurofibromatosis. Type 1 (NF-1), also called von Recklinghausen's disease, causes multiple benign (noncancerous) tumors of the nerves and skin. Type 2 (NF-2) causes benign tumors of the nerves that transmit sound from the inner ears to the brain. In some cases, NF-2 causes visions problems and increases the risk of developing specific brain and spinal cord tumors. NF-1 can also cause a change in the color of the skin. Areas of unusual skin color may appear on the trunk of the body as well as cause freckling under the arms or in the groin area. Abnormal skin color may be seen in the patient by one year of age, and the area affected gets bigger over time.
At birth or early childhood, patients may have rather large benign tumors that consist of bundles of nerves. They may also develop harmless tumor-like nodules of the colored parts of the eyes or tumors of the optic nerves, which send nerve impulses from the innermost membrane of the eyes (retinas) to the brain. More rarely, patients may develop certain malignant (cancerous) tumors.
NF-1 may also cause the head to become unusually large and the body to be short. Other symptoms, which can vary greatly from case to case, may include seizures, curvature of the spine, learning problems, speech difficulties, hyperactivity, bowed legs and poor bone development.
Symptoms of NF-2 may show up during childhood, adolescence or early adulthood. Depending on the location and size of the tumors, other symptoms may include problems with balance and walking; dizziness; headache; facial weakness, numbness or pain; ringing in the ears; and/or progressive hearing loss. In some cases, NF-2 causes vision problems and heightens the risk of developing specific brain and spinal cord tumors.
Causes and Risk Factors
NF-1 is caused by changes in a gene that controls production of a protein. This gene is believed to work as a tumor suppressor. In about 50% of individuals with NF-1, the disorder results from gene mutations that happen for unknown reasons. In others with the disorder, NF-1 is an inherited trait.
NF-2 results from changes in a different tumor-suppressing gene. As with NF-1, some people with NF-2 experience a gene mutation that occurs for reasons unknown, while others inherit the trait.