NF1 is a hereditary disorder due to an alteration, called a mutation, in the NF1 gene. All people have two copies of every gene, one copy inherited from each parent. The NF1 gene mutation is dominant, meaning only one of the two copies of the gene needs to have the mutation to produce the disorder. A parent with NF1 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. The Inheritance animation below illustrates how this occurs.