Neurofibromatosis can either be an inherited disorder or the product of a gene mutation. Both NF1 and NF2 are caused by two separate abnormal genes and may be inherited from parents who have NF or may be the result of a mutation in the sperm or egg cells. NF is considered an autosomal dominant disorder because the gene is located on one of the 22 chromosome pairs, called autosomes.The gene for NF1 is located on chromosome 17.
The gene for NF2 is located on chromosome 22. Children have a 50 percent chance of inheriting the genes that cause NF if the parent has NF. The type of NF the child inherits will be the same as that of the parent. Therefore, if the parent has NF1, there will be a 50 percent chance the child will have NF1. If the parent has NF2, there will be a 50 percent chance the child will have NF2.
The only difference between the child and the parent in these circumstances is the severity of NF and the appearance of symptoms. The presence of only one changed or affected gene can cause the disorder to appear. However, the action of the unaffected gene that is paired with the dominant gene does not prvent the disorder from appearing. People with NF can make two different kinds of reproductive cells: one that can cause a child to have NF and the other that will produce an unaffected child, if that is the gene that happens to be used. When an unaffected individual conceives a child with a person with NF, there are four possible cell combinations - two combinations that will yield a child with NF and the other two that will yield an unaffected child.