Indeed, it is known that the phenotype of CMT caused by heterozygous expression of T118M PMP22 is similar in symptoms to HNPP (16, 18), as expected given that the total amount of PMP22 that reaches the cell surface under WT/null conditions is similar to that occurring under WT/T118M conditions. This evidence concerns the gene PMP22 and Charcot-Marie-Tooth disease.