Neurofibromatosis type 1 - Causes of neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is caused by a genetic mutation in a gene called the NF1 gene.

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

The NF1 gene is responsible for producing a protein that helps regulate the growth of nerve tissue. The protein effectively "switches off" the growth of tissue once it has reached a certain size.

However, the mutation causes some of the instructions inside the body’s cells to become scrambled. This leads to the cells producing an incomplete protein that is much less effective at switching off the growth of nerve tissue, leading to multiple areas of uncontrolled growth (tumours) developing in the nervous system.

The faulty gene that causes NF1 is found on chromosome number 17.

How it's inherited

In around half of all cases of NF1, the mutated gene is passed down from a parent to their child.

The NF1 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 that they have will develop NF1. Males and females have the same chance of developing the condition.

The severity of the condition is not always inherited. For example, a child may have mild NF1 even if they inherited the condition from one of their parents who is more severely affected.

Sporadic mutation

In around half of NF1 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 NF1 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 NF1 sporadically can pass the condition to their children. The chances of this happening are the same as for someone who inherited the condition themselves (see above).