Coexistence of Charcot-Marie-Tooth 1A and nondystrophic myotonia due to PMP22 duplication and SCN4A pathogenic variants: a case report.

BACKGROUND: Charcot-Marie-Tooth disease (CMT) is a genetically heterogeneous hereditary neuropathy, and CMT1A is the most common form; it is caused by a duplication of the peripheral myelin protein 22 (PMP22) gene. Mutations in the transient sodium channel Nav1.4 alpha subunit (SCN4A) gene underlie a diverse group of dominantly inherited nondystrophic myotonias that run the spectrum from subclinical myopathy to severe muscle stiffness, disabling weakness, or frank episodes of paralysis. CASE PRESENTATION: We describe a Chinese family affected by both CMT1A and myotonia with concomitant alterations in both the PMP22 and SCN4A genes. In this family, the affected proband inherited the disease from his father in an autosomal dominant manner. Genetic analysis confirmed duplication of the PMP22 gene and a missense c.3917G > C (p. Gly1306Ala) mutation in SCN4A in both the proband and his father. The clinical phenotype in the proband showed the combined involvement of skeletal muscle and peripheral nerves. Electromyography showed myopathic changes, including myotonic discharges. MRI revealed the concurrence of neurogenic and myogenic changes in the lower leg muscles. Sural nerve biopsies revealed a chronic demyelinating and remyelinating process with onion bulb formations in the proband. The proband's father presented with confirmed subclinical myopathy, very mild distal atrophy and proximal hypertrophy of the lower leg muscles, pes cavus, and areflexia. CONCLUSION: This study reports the coexistence of PMP22 duplication and SCN4A mutation. The presenting features in this family suggested that both neuropathy and myopathy were inherited in an autosomal dominant manner. The proband had a typical phenotype of sodium channel myotonia (SCM) and CMT1A. However, his father with the same mutations presented a much milder clinical phenotype. Our study might expand the genetic and phenotypic spectra of neuromuscular disorders with concomitant mutations.

Novel GARS mutation presenting as autosomal dominant intermediate Charcot-Marie-Tooth disease.

We report the first family with a glycyl-tRNA synthetase (GARS) mutation with autosomal dominant intermediate Charcot-Marie-Tooth disease (DI-CMT). The proband and the proband's father presented with gait disturbance and hand weakness. Both patients displayed moderately decreased conduction velocities (MNCV) (ranging from 29.2 to 37.8 m/s). A sural nerve biopsy of the father revealed evidence of both axonal loss and demyelination. On exome sequencing, in both the proband and his father, we identified a novel missense mutation (c.643G > C, p.Asp215His) in the GARS gene in a heterozygous state, which is considered to be pathogenic for this DI-CMT family. The present study broadens current knowledge about intermediate CMT and the phenotypic spectrum of defects associated with GARS.

MFN2-related Charcot-Marie-Tooth Disease with Atypical Ocular Manifestations.

We herein describe a Charcot-Marie-Tooth disease (CMT) family with a MFN2 mutation with atypical ocular manifestations. The proband, his mother, his third daughter, and his deceased maternal grandfather all had symptoms of CMT and a visual impairment (either cataracts or severe astigmatism). On whole-exome sequencing for the proband having CMT and congenital cataracts, we identified a c.314C>T (p.Thr105Met) mutation in MFN2, but no mutation in the causative genes associated with cataracts. This missense mutation in MFN2 co-segregated with CMT and the atypical ocular manifestations in this family. The findings of this study might help to expand the clinical phenotype of heterogeneous MFN2-related CMT.