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      Recurrent episodes of reversible posterior leukoencephalopathy in three Chinese families with GJB1 mutations in X-linked Charcot-Marie-tooth type 1 disease: cases report

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          Abstract

          Background

          The X-linked form of Charcot-Marie-Tooth disease type 1 (CMTX1) is an inherited peripheral neuropathy that arises in patients with mutations in the gap-junction beta-1 gene (GJB1).

          Case presentation

          Three young male patients from Southern China with pes cavus experienced multiple episodes of transient central nervous system (CNS) dysfunction. Three patients all had reversible posterior leukoencephalopathy as detected by brain diffusion-weighted magnetic resonance imaging (MRI-DWI). Nerve conduction velocity (NCV) showed sensorimotor polyneuropathy with mixed demyelinating and axonal features. Genetic testing indicated a c.425G > A (p.Arg142Glu) or c.563 C > T (p.Thr188Ile) or c.103G > C (p.Val35Leu) mutation in GJB1. The unique feature of this report is the identification of two novel mutations: c.563 C > T and sc.103G > C of the GJB1 gene detected in two families respectively. Another unique feature is that peripheral neuropathy symptoms in the three patients were insidious and found at the onset of CNS symptoms.

          Conclusions

          Posterior leukoencephalopathy is involved in CMTX1 patients. The white matter changes in MRI of CMTX1 patients are reversible and recover later than CNS symptoms.

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          Most cited references23

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          Connexin mutations in X-linked Charcot-Marie-Tooth disease.

          X-linked Charcot-Marie-Tooth disease (CMTX) is a form of hereditary neuropathy with demyelination. Recently, this disorder was mapped to chromosome Xq13.1. The gene for the gap junction protein connexin32 is located in the same chromosomal segment, which led to its consideration as a candidate gene for CMTX. With the use of Northern (RNA) blot and immunohistochemistry technique, it was found that connexin32 is normally expressed in myelinated peripheral nerve. Direct sequencing of the connexin32 gene showed seven different mutations in affected persons from eight CMTX families. These findings, a demonstration of inherited defects in a gap junction protein, suggest that connexin32 plays an important role in peripheral nerve.
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            Connexins are critical for normal myelination in the CNS.

            Mutations in Cx32, a gap-junction channel-forming protein, result in X-linked Charcot-Marie-Tooth disease, a demyelinating disease of the peripheral nervous system. However, although oligodendrocytes express Cx32, central myelination is unaffected. To explore this discrepancy, we searched for additional oligodendrocyte connexins. We found Cx47, which is expressed specifically in oligodendrocytes, regulated in parallel with myelin genes and partially colocalized with Cx32 in oligodendrocytes. Mice lacking either Cx47 or Cx32 are viable. However, animals lacking both connexins die by postnatal week 6 from profound abnormalities in central myelin, characterized by thin or absent myelin sheaths, vacuolation, enlarged periaxonal collars, oligodendrocyte cell death, and axonal loss. These data provide the first evidence that gap-junction communication is crucial for normal central myelination.
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              Transient central nervous system white matter abnormality in X-linked Charcot-Marie-Tooth disease.

              X-linked Charcot-Marie-Tooth disease (CMTX) is a hereditary demyelinating neuropathy caused by mutations in the connexin 32 (Cx32) gene. Cx32 is widely expressed in brain and peripheral nerve, yet clinical manifestations of CMTX mainly arise from peripheral neuropathy. We have evaluated two male patients with CMTX who on separate occasions developed transient ataxia, dysarthria, and weakness within 3 days of returning from ski trips at altitudes above 8,000 feet. Magnetic resonance imaging studies in both patients showed nonenhancing, confluent, and symmetrical white matter abnormalities that were more pronounced posteriorly and that resolved over several months. Magnetic transfer images in one patient demonstrated increased magnetization transfer ratios distinct from that seen in demyelination or edema. Both patients returned to their normal baseline within 2 to 3 weeks. These cases suggest that CMTX patients are at risk for developing an acute, transient, neurological syndrome when they travel to places at high altitudes and return to sea level. Cx32 mutations may cause central nervous system dysfunction by reducing the number of functioning gap junctions between oligodendrocytes and astrocytes, making both cells more susceptible to abnormalities of intercellular exchange of ions and small molecules in situations of metabolic stress.
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                Author and article information

                Contributors
                hwen1229@163.com
                Journal
                BMC Neurol
                BMC Neurol
                BMC Neurology
                BioMed Central (London )
                1471-2377
                16 December 2019
                16 December 2019
                2019
                : 19
                : 325
                Affiliations
                ISNI 0000 0004 1798 2653, GRID grid.256607.0, Department of Neurology, First Affiliated Hospital, , Guangxi Medical University, ; #6 Shuangyong Road, Nanning, Guangxi People’s Republic of China 530021
                Author information
                http://orcid.org/0000-0002-9055-9873
                Article
                1563
                10.1186/s12883-019-1563-4
                6912941
                31842800
                87cf7565-ea30-49c2-8a81-2a6f92741353
                © The Author(s). 2019

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 17 July 2019
                : 9 December 2019
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100004607, Natural Science Foundation of Guangxi Province;
                Award ID: 2017GXNSFAA198042
                Categories
                Case Report
                Custom metadata
                © The Author(s) 2019

                Neurology
                x-linked form of charcot-marie-tooth disease type 1,gap-junction beta-1 gene,reversible posterior leukoencephalopathy

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