A novel point mutation in the PMP22 gene in a family with Roussy-Levy syndrome

Peripheral Myelin Protein 22 Gene Mutations in Charcot-Marie-Tooth Disease Type 1E Patients

Duplication and deletion of the peripheral myelin protein 22 (PMP22) gene cause Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP), respectively, while point mutations or small insertions and deletions (indels) usually cause CMT type 1E (CMT1E) or HNPP. This study was performed to identify PMP22 mutations and to analyze the genotype−phenotype correlation in Korean CMT families. By the application of whole-exome sequencing (WES) and targeted gene panel sequencing (TS), we identified 14 pathogenic or likely pathogenic PMP22 mutations in 21 families out of 850 CMT families who were negative for 17p12 (PMP22) duplication. Most mutations were located in the well-conserved transmembrane domains. Of these, eight mutations were not reported in other populations. High frequencies of de novo mutations were observed, and the mutation sites of c.68C>G and c.215C>T were suggested as the mutational hotspots. Affected individuals showed an early onset-severe phenotype and late onset-mild phenotype, and more than 40% of the CMT1E patients showed hearing loss. Physical and electrophysiological symptoms of the CMT1E patients were more severely damaged than those of CMT1A while similar to CMT1B caused by MPZ mutations. Our results will be useful for the reference data of Korean CMT1E and the molecular diagnosis of CMT1 with or without hearing loss.

Charcot-Marie-Tooth disease: an overview of genotypes, phenotypes, and clinical management strategies

Charcot-Marie-Tooth (CMT) disease, which encompasses several hereditary motor and sensory neuropathies, is one of the most common neuromuscular disorders. Our understanding of the molecular genotypes of CMT and the resultant clinical and electrophysiological phenotypes has increased greatly in the past decade. Characterized by electrodiagnostic studies into demyelinating (type 1) and axonal (type 2) forms, subsequent genetic testing often provides an exact diagnosis of a specific subtype of CMT. These advancements have made diagnostic paradigms fairly straightforward. Still, the nature and extent of neuromuscular disability is often complex in persons with CMT, and no curative treatments are yet available. Genotypically homologous animal models of CMT have improved exploration of disease-modifying treatments, of which molecular genetic manipulation and stem cell therapies appear to be the most promising. Research is also needed to develop better rehabilitative strategies that may limit disease burden and improve physical performance and psychosocial integration. Clinical management should be multidisciplinary, including neurologists, physiatrists, neurogeneticists, neuromuscular nurse practitioners, and orthopedists, along with physical and occupational therapists, speech-language pathologists, orthotists, vocational counselors, social workers, and other rehabilitation clinicians. Goals should include maximizing functional independence and quality of life while minimizing disability and secondary morbidity.