Neurofibromatosis type 2
What is neurofibromatosis type 2?
Neurofibromatosis type 2 is a disorder in which noncancerous tumours called vestibular schwannomas or acoustic neuromas develop along nerves in the inner ear. tumours can also occur on nerves in other areas of the brain or spinal cord.
Signs and symptoms usually appear during adolescence or in a person's early twenties. The most common early symptoms are hearing loss, ringing in the ears (tinnitus), and problems with balance, which are caused by tumours growing on nerves that lead from the ear to the brain. If tumours develop in other parts of the brain or spinal cord, signs and symptoms vary according to the tumour's location. They can include seizures, changes in vision or sensation, numbness or weakness in the arms or legs, and fluid buildup in the brain. Some people with neurofibromatosis type 2 also develop clouding of the lens in the eye (cataracts) at an early age.
How common is neurofibromatosis type 2?
Neurofibromatosis type 2 affects about 1 in 40,000 people.
What genes are related to neurofibromatosis type 2?
Mutations in the NF2 gene cause neurofibromatosis type 2.
The NF2 gene provides instructions for making a protein called merlin (also known as schwannomin). This protein is produced in the nervous system, particularly in Schwann cells, which surround and insulate nerve cells in the brain and spinal cord. Merlin acts as a tumour suppressor, which means that it keeps cells from growing and dividing too rapidly or in an uncontrolled way. Although its exact function is unknown, this protein is likely also involved in controlling cell movement, cell shape, and communication between cells. Mutations in the NF2 gene lead to the production of a nonfunctional version of the merlin protein that cannot regulate the growth and division of cells. Research suggests that the loss of merlin allows cells—especially Schwann cells—to multiply too frequently and form the tumours characteristic of neurofibromatosis type 2.
How do people inherit neurofibromatosis type 2?
Neurofibromatosis type 2 is considered to have an autosomal dominant pattern of inheritance. People with this condition are born with one mutated copy of the NF2 gene in each cell. In about half of cases, the altered gene is inherited from an affected parent. The remaining cases are the result of new mutations in the NF2 gene, and occur in people with no history of the disorder in their family.
Unlike most other autosomal dominant conditions, in which one altered copy of a gene in each cell is sufficient to cause the disorder, two copies of the NF2 gene must be altered to trigger tumour formation in neurofibromatosis type 2. A mutation in the second copy of the NF2 gene occurs in Schwann cells during a person's lifetime. Almost everyone who is born with one NF2 mutation acquires a second mutation in many cells and develops the tumours characteristic of neurofibromatosis type 2.
What other names do people use for neurofibromatosis type 2?
* BANF
* Bilateral Acoustic Neurofibromatosis
* Familial Acoustic Neuromas
* Neurofibromatosis 2
* Neurofibromatosis Type II
* NF2
* Schwannoma, Acoustic, Bilateral
