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Clinical and Genetic Features of Biallelic Mutations in SORD in a Series of Chinese Patients With Charcot-Marie-Tooth and Distal Hereditary Motor Neuropathy

ABSTRACT: Biallelic mutations in the sorbitol dehydrogenase (SORD) gene have recently been found to be one of the most frequent causes of autosomal recessive axonal Charcot-Marie-Tooth (CMT2) and distal hereditary motor neuropathy (dHMN). This study was performed to explore the frequency of SORD mutations and correlations of the phenotypic-genetic spectrum in a relatively large Chinese cohort. In this study, we screened a cohort of 485 unrelated Chinese patients with hereditary neuropathy by using Sanger sequencing, next generation sequencing, or whole exome sequencing after PMP22 duplication was initially excluded. SORD mutation was identified in five out of 78 undiagnosed patients. Two individuals carried the previously reported homozygous c.757 delG (p.A253Qfs*27) variant, and three individuals carried the heterozygous c.757delG (p.A253Qfs*27) variant together with a second novel likely pathogenic variant, including c.731 C>T (p.P244L), c.776 C>T (p.A259V), or c.851T>C (p.L284P). The frequency of SORD variants was calculated to be 6.4% (5/78) in unclarified CMT2 and dHMN patients. All patients presented with distal weakness and atrophy in the lower limb, two of whom had minor clinical sensory abnormalities and small fiber neuropathy. Our study provides further information on the genotype and phenotype of patients with SORD mutations.

SUBMITTER: Liu X

PROVIDER: S-EPMC8607551 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Dominant intermediate Charcot-Marie-Tooth neuropathy type B is caused by mutations in dynamin 2. We studied the clinical, haematological, electrophysiological and sural nerve biopsy findings in 34 patients belonging to six unrelated dominant intermediate Charcot-Marie-Tooth neuropathy type B families in whom a dynamin 2 mutation had been identified: Gly358Arg (Spain); Asp551_Glu553del; Lys550fs (North America); Lys558del (Belgium); Lys558Glu (Australia, the Netherlands) and Thr855_Ile856del (Belgium). The Gly358Arg and Thr855_Ile856del mutations were novel, and in contrast to the other Charcot-Marie-Tooth-related mutations in dynamin 2, which are all located in the pleckstrin homology domain, they were situated in the middle domain and proline-rich domain of dynamin 2, respectively. We report the first disease-causing mutation in the proline-rich domain of dynamin 2. Patients with a dynamin 2 mutation presented with a classical Charcot-Marie-Tooth phenotype, which was mild to moderately severe since only 3% of the patients were wheelchair-bound. The mean age at onset was 16 years with a large variability ranging from 2 to 50 years. Interestingly, in the Australian and Belgian families, which carry two different mutations affecting the same amino acid (Lys558), Charcot-Marie-Tooth cosegregated with neutropaenia. In addition, early onset cataracts were observed in one of the Charcot-Marie-Tooth families. Our electrophysiological data indicate intermediate or axonal motor median nerve conduction velocities (NCV) ranging from 26 m/s to normal values in four families, and less pronounced reduction of motor median NCV (41-46 m/s) with normal amplitudes in two families. Sural nerve biopsy in a Dutch patient with Lys558Glu mutation showed diffuse loss of large myelinated fibres, presence of many clusters of regenerating myelinated axons and fibres with focal myelin thickenings--findings very similar to those previously reported in the Australian family. We conclude that dynamin 2 mutations should be screened in the autosomal dominant Charcot-Marie-Tooth neuropathy families with intermediate or axonal NCV, and in patients with a classical mild to moderately severe Charcot-Marie-Tooth phenotype, especially when Charcot-Marie-Tooth is associated with neutropaenia or cataracts.

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Clinical and Genetic Features of Biallelic Mutations in SORD in a Series of Chinese Patients With Charcot-Marie-Tooth and Distal Hereditary Motor Neuropathy

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