Neurofibromatosis

The Facts

Neurofibromatosis (NF) is a genetic disorder that affects the nervous system. People affected by this condition develop non-cancerous tumours along their nerves. The tumours are called neurofibromas. They are a mass of different types of cells that grow on and surround nerves.

NF can also cause skin discolorations (also called “café au lait” spots) and bone abnormalities. Men, women, and people of all ethnic backgrounds may develop the condition.

Causes

The cause of NF is a change in a person’s genetic material, known as a genetic mutation. There are two genes that cause two different types of NF: neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2). NF1 was previously known as von Recklinghausen’s disease and occurs more commonly than NF2.

NF is a genetic condition. If either parent has the gene for NF, their child will have a 50% chance of inheriting the disease. Sometimes the gene may change spontaneously in an individual who has no family history of the condition. Once the gene changes, NF may be passed on to the next generation.

Symptoms and Complications

The symptoms related to NF1 and NF2 are different.

People with NF1 may have some of the following symptoms:

• noncancerous tumours under the skin (or deeper within the body)
• brown patches in the iris (coloured part of the eye) called Lisch nodules
• bowed legs, short stature, or bone abnormalities including scoliosis (an abnormal side-to-side curve in the spine)
• freckles in the groin or underarm area
• growth of a tumour on the optic nerve (an optic glioma)
• light brown flat skin marks called “café au lait” spots

Because it affects the nervous system, NF1 may cause learning disabilities, speech problems, and delays in an individual’s development. Seizures, eye tumours, and high blood pressure may also affect people with this condition. Rarely, the tumours may become malignant (cancerous). In some cases, tumours may also affect organs within the body.

People with NF2 develop tumours that appear on the nerve that connects the ear to the brain. These tumours are also called “schwannomas.” Because of their association with the ear, tumours on this nerve may cause hearing difficulties. Other complications related to the ear may include dizziness, ringing in the ears (tinnitus), and balance problems. The pressure from the tumours on other nerves may also cause headaches or numbness of the face or weakened facial muscles.

People who have NF2 may also develop tumours in other body areas, such as the brain and spinal cord. Unlike NF1, skin discoloration and freckles are few or nonexistent in people with NF2. Cataracts can develop early in life, which may cause vision difficulties or blindness.

Making the Diagnosis

To make the diagnosis, your doctor will do a number of tests and examinations.For NF1, a doctor will discuss your medical history and do a physical examination of your skin to look for “café au lait” spots and freckling. X-rays will help your doctor look for abnormalities in your bone structure.

Doctors usually request tests that confirm tiny tumours on the nerves in both NF1 and NF2. MRI scans may reveal tumours in various parts of the body. Blood tests may also be done to screen for the NF gene. When NF2 is suspected, the doctor may recommend hearing tests to evaluate a person’s hearing and the function of the nerve that leads from the ear to the brain