Neurofibromatosis 1 (NF1), also known as von Recklinghausen disease, is caused by mutations of the NF1 gene, which is located at chromosome 17q11.2.

• A wide variety of NF1 mutations have been found in patients with NF1. No frequently recurring mutation has been identified.

• Diagnosis of NF1 is based on established clinical criteria.

• Average life expectancy of patients with NF1 is probably reduced by at least 10 to 15 years, with malignancy as the most common cause of death.

• Substantial variability in expression of NF1 features occurs, even in affected members of a single family.

• Laboratory testing for NF1 mutations is difficult. A protein truncation test is commercially available, but its sensitivity, specificity, and predictive value have not been established.

• The prevalence of clinically diagnosed NF1 ranges from 1/2,000 to 1/5,000 in most population-based studies.

Results published in: American Journal of  Epidemiology 2000;151:33-40.