The following information may help to address your question:
The National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health (NIH), has an information page on neurofibromatosis.
You can also contact NINDS for information on neurofibromatosis:
NIH Neurological Institute
P.O. Box 5801
Bethesda, MD 20824
E-mail form: http://www.ninds.nih.gov/contact_us.htm
Web site: http://www.ninds.nih.gov/