What percentage of neurofibromatosis is random, in which no family members have it but you?

About half: Neurofibromatosis type 1, also known as nf1 or von recklinghausen's disease, is caused by alterations to a gene on chromosome 17. These mutations can be passed from parent to child or, about 50% of the time, they happen as a new event in the dna of either the egg or the sperm before fertilization. It's always wise, when 1 person is diagnosed with nf1, to have all of their close relatives examined.

Rare: Non genetic mutation, causing neurofibromatosis is rare. In nf-1 chromosome 17 is involved nf-2 chro. 22 is involved, autosomal dominant transmission that means 50% chances the offspring will inherit the disease.

Fifty percent: Estimated incidence of NF1 is 1 in 3000. Approximately half of affected individuals represent first cases in the family as a result of a new genetic event or mutation. Therefore 1 in 1500 are new cases.