Is neurofibromatosis a polygenic disorder, or is there a single mutation?

Single gene disorder: Neurofibromatosis type 1 is caused by a mutation of the nf1 gene on chromosome 17. This gene normally allows your cells to make a protein called neurofibromin. So far we have found more than 500 different mutations in this gene in people with this condition. You just need one mutation to get nf1 - half the time it comes out of the blue, and half the time it's inherited from a parent.

Neurofibromatosis: Nf type 1 is caused by mutation on chromosome 17, nf type 2 is due to mutation on chromosome 22. Both nf-1 and nf-2 are autosomal dominant disorders, meaning only one copy of the mutated gene need be inherited to pass the disorder. A child of a parent with nf-1 or nf-2 will have a 50–100% chance of inheriting the disorder. Both nf-1 and nf-2 can also appear as spontaneous mutations.