GJB1 and Charcot-Marie-Tooth disease: MFN2 mutations comprise ∼6% of familial CMT (∼22% of familial CMT2) (Bombelli et al., 2014; Choi et al., 2015) and are, depending upon nationality, the second or third most common cause of CMT, after the PMP22 duplication/deletion and GJB1 mutations that cause CMT1A (Fridman et al., 2015; Ando et al., 2017; Hoebeke et al., 2018; Yoshimura et al., 2019).