Expanding the Clinical Spectrum of <i>DRP2</i>-Associated Charcot-Marie-Tooth Disease.

Abstract

Germline truncating variants in the <i>DRP2</i> gene (encoding dystrophin-related protein 2) cause the disruption of the periaxin-DRP2-dystroglycan complex and have been linked to Charcot-Marie-Tooth disease. However, the causality and the underlying phenotype of the genetic alterations are not clearly defined. This cross-sectional retrospective observational study includes 9 patients with Charcot-Marie-Tooth disease (CMT) with <i>DRP2</i> germline variants evaluated at 6 centers throughout Spain. We identified 7 Spanish families with 4 different <i>DRP2</i> likely pathogenic germline variants. In agreement with an X-linked inheritance, men harboring hemizygous <i>DRP2</i> variants presented with an intermediate form of CMT, whereas heterozygous women were asymptomatic. Symptom onset was variable (36.6 ± 16 years), with lower limb weakness and multimodal sensory loss producing a mild-to-moderate functional impairment. Nerve echography revealed an increase in the cross-sectional area of nerve roots and proximal nerves. Lower limb muscle magnetic resonance imaging confirmed the presence of a length-dependent fatty infiltration. Immunostaining in intradermal nerve fibers demonstrated the absence of DRP2 and electron microscopy revealed abnormal myelin thickness that was also detectable in the sural nerve sections. Our findings support the causality of <i>DRP2</i> pathogenic germline variants in CMT and further define the phenotype as a late-onset sensory and motor length-dependent neuropathy, with intermediate velocities and thickening of proximal nerve segments.