Neurofibromatosis type 1 (NF1) is a common tumor predisposition syndrome affecting 1 in 2,500 persons worldwide.1 Mutations in the NF1 gene, which causes NF1, have been identified in each of the 60 exons, with more than 2,800 mutations identified to date.2 The high mutation rate and size of the NF1 gene disfavor strong genotype-phenotype correlations. The gene discussed is NF1; the disease is neurofibromatosis type 1.