Neurofibromatosis type 2 - Causes of neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is caused by a genetic mutation in a gene called the NF2.

Genes are the instructions that are used to produce all human characteristics.

The NF2 gene produces a protein called merlin (also called schwannomin). This protein plays an important role in regulating the growth of nerve tissue.

However, the mutation causes some of the instructions inside the body’s cells to become scrambled. This results in the cells producing an incomplete protein, or no protein at all. Without an effective merlin protein, multiple areas of uncontrolled growth (tumours) can develop in the nervous system.

The faulty gene that causes NF2 is found on chromosome number 17.

How it's inherited

In around half of all cases of NF2, the mutated gene is passed down from a parent to their child.

The NF2 mutation is known as an autosomal dominant mutation. This means only one parent has to have the faulty gene for a child to be at risk of developing the condition.

If either the mother or father has the faulty gene, there is a one in two chance each child they have will develop NF2.

Males and females have the same chance of developing the condition.

Sporadic mutation

In around half of NF2 cases, the mutation appears to occur in either the sperm or egg just before conception. This is known as a sporadic mutation. It is unclear what causes it or whether anything increases the risk of it happening.

If you have a child who develops NF2 as a result of a sporadic mutation, it is highly unlikely any further children you have will also develop the condition.

A person who develops NF2 sporadically can pass the condition to their children. The chances of this happening are usually the same as those for someone who inherited the condition (see above), unless they develop a form of NF2 called mosaic NF2 (see below).

Read more about genetics.

Mosaic NF2

In about one third of cases, NF2 takes a mild form called mosaic NF2.

Mosaic NF2 develops when the mutation occurs after an embryo has been conceived. This is different from "normal" NF2, where the mutation is already present in the sperm or the egg before conception takes place.

As the mutation takes place later in the development of the embryo, not all the cells of the body are affected in mosaic NF2. Therefore, the symptoms of mosaic NF2 are milder and are often restricted to a certain area or side of the body.

As the genetic mutation is not present in all the cells of someone with mosaic NF2, the risk of someone with this form of the condition having a child with NF2 is less than the usual 50%. However, if the child of someone with mosaic NF2 is affected, the child will have the normal – and more severe – form of the condition.