A novel family with axonal Charcot-Marie-Tooth disease caused by a mutation in the EGR2 gene

EGR2 (Early Growth Response 2) is one of the most important transcription factors involved in myelination in the peripheral nervous system. EGR2 mutations typically cause different forms of demyelinating neuropathy, that is, Charcot-Marie-Tooth type 1D (CMT1D), Dejerine-Sottas Syndrome (DSS), and Congenital Hypomyelinating Neuropathy (CHN). However, the EGR2 gene has been recently associated with an axonal phenotype (CMT2) in a large CMT family. Here, we report another CMT family exhibiting an axonal phenotype associated with a missense change (c.1235A>G, p.E412G) in the EGR2 gene. Neurological evaluation of five affected members of the family showed a classical CMT phenotype including distal muscle atrophy and weakness, absence of deep tendon reflexes, pes cavus, and scoliosis. Electrophysiological examination was consistent with a motor-sensory axonal neuropathy. Sural nerve biopsy performed in one patient showed a loss of myelinated and unmyelinated nerve fibers without de-remyelinating signs and onion bulbs. This study confirms the phenotypical heterogeneity of EGR2-related neuropathy, indicating a role for EGR2 in primary axonal degeneration.