A case of two siblings with CMT1 showed a deletion in PMP22 exon 4 has recently been reported [69], showing how the deletion of this exon causes a segregation of PMP22 to the endoplasmic reticulum instead of localizing the protein to the plasma membrane, contributing to the pathogenesis of CMT1 (Fig. 5a). Here, PMP22 is linked to Charcot-Marie-Tooth disease type 1.