EGR2-related mixed demyelinating and axonal Charcot-Marie-Tooth disease: An electrodiagnostic, nerve imaging, and histological study

Abstract

The early growth response 2 gene (EGR2) mutations are associated with a group of hereditary neuropathy, including axonal neuropathy and hypomyelinating neuropathy or Charcot-Marie-Tooth disease (CMT) type 1D. We aim to perform an electrodiagnostic, nerve imaging, and histological study of EGR2-associated neuropathy. We performed a retrospective analysis of two patients with EGR2-related neurology at our hospital. The neuropathy was confirmed by the nerve conduction study. Nerve imaging and sural biopsies were performed in two patients. Two unrelated boys exhibited early-onset length-dependent neuropathy. Next generation sequencing identified EGR2 gene with previously described E412K mutation in the third zine finger domain in patient 1 and a previously undescribed variant D355N mutation in the first zinc finger domain in patient 2. The magnetic resonance imaging of the lumbosacral plexus showed no abnormalities in patient 1 and thickened lumbosacral plexuses in patient 2. Electrophysiology and nerve biopsies showed a prominent axonal neuropathy, accompanied with demyelinating involvement. Therefore, it seemed that the EGR2 mutations could cause not only the known demyelinating type and axonal type but also mixed-type CMT. Our findings expanded the phenotypic heterogeneities of EGR2-associated neuropathy.