NF1 and plexiform neurofibroma: Two types of constitutional NF1 mutations have been found to influence neurofibroma number: Type-1 deletions (1.4-Mb deletions with breakpoints located within NF1-REPs a and c) seem to be associated with the early onset of a large number of dNFs [Kayes et al., 1994; Wu et al., 1995] and the c.2970-2972 delAAT mutation has been identified in patients with an absence of dNFs [Upadhyaya et al., 2007].