For example, in neurofibromatosis type 1, even if most of the affected individuals are carriers of a germinal mutation in the NF1 gene and develop a complete disease phenotype, some individuals were reported to have clinical manifestations limited to a tissue or an organ due to the presence of post-zygotic mutations in the NF1 gene (Biesecker and Spinner 2013; Kaplan et al. 2010). This evidence concerns the gene NF1 and neurofibromatosis type 1.