Neurofibromatosis type 2 is caused by a change in the NF2 gene located on chromosome 22. This gene encodes a protein known as merlin. Mutations in the NF2 gene disrupt the function of merlin, which is part of a complex molecular signaling pathway that regulates how cells grow and divide.

Inherited Mutations

All people have two copies of every gene – one copy inherited from each parent. The NF2 gene mutation is dominant, which means that only one of the two copies of the gene needs to have the mutation to produce the disorder in an individual. A parent with NF2 has a 50% chance of passing the abnormal gene copy to a child. A child who inherits the altered gene will also have the disorder.

Spontaneous Mutations

About 50% of people with NF2 appear to be the first members of their family have the disorder. In these cases, the genetic alteration, or mutation, occurred in the sperm or egg cell that formed the individual with NF2. This is called a spontaneous, or new, mutation. A person with a spontaneous mutation of the NF2 has a 50% chance of passing the abnormal gene copy to a child.

Genetic testing is currently available to confirm the presence of the NF2 gene mutation with 90% sensitivity and may be appropriate in some cases. Like with NF1, some people with NF2 have features of the disorder that are limited to only one part or one side of their body. This is called mosaic NF2 (also called segmental NF2). Mosaic NF2 is caused by a gene mutation. Genetic testing for people with this type of NF, while possible, can be more complex than for individuals who do not have this form of the disorder and may require genetic testing of tumor tissue.>