NF1 and neurofibromatosis type 1: The issue of genotype/phenotype correlations in Neurofibromatosis type I is further complicated by the mechanism of action of the NF1 gene, which acts as an oncosuppressor through the combination of a constitutional variant (inherited or de novo) and a somatic, acquired inactivation of the other allele for the initiation of the molecular cascade in most of the affected tissues.20, 21