The generally mild CMT phenotype associated with heterozygous expression of T118M suggests that reduced cell surface trafficking of a single PMP22 allele is insufficient to cause the more severe neuropathy and dysmyelination that is associated with both overexpressed WT PMP22 (CMT1A) and with a number of other disease mutant forms of PMP22, such as L16P (causing DSS or CMTE). The gene discussed is PMP22; the disease is neuropathy.