All children and adolescents with genetically proven Charcot Marie Tooth neuropathy (CMT) 1a (gene: PMP 22 duplication), CMT1b (MPZ), CMT4c (SH3TC2), and CMT4d (NDRG1), which are all hereditary neuropathies with demyelination; were also revealed to have enlarged nerves, the majority of them present in most segments compared to the age-matched reference values. This evidence concerns the gene MPZ and Charcot-Marie-Tooth disease, axonal, type 2FF.