X-linked Charcot-Marie-Tooth disease type 1 (CMTX1) is a rare inherited neuropathy caused by mutations in the GJB1 gene, leading to progressive distal muscle weakness and atrophy. In this case study, a 37-year-old man presented with recurrent episodes of numbness involving the lips, right hand, and foot, followed by right-sided limb weakness and dysarthria four times over the past 20 years. Notably, the last three episodes were consistently triggered within 3 days after descent to sea level following exposure to high-altitude environments (8,500-10,000 feet, with transit above 13,000 feet). Based on the neurologic examination, brain magnetic resonance imaging (MRI), and genetic testing, the patient was diagnosed with X-linked Charcot-Marie-Tooth disease. This case underscores the importance of considering high-altitude exposure as a potential trigger and highlights the value of GJB1 testing in young patients presenting with acute stroke-like episodes and signs of peripheral neuropathy.

The patient is a 17-year-old male. He had a history of hospitalization for influenza at the age of 11, and Brain MRI at that time showed reversible brain lesions in the splenium of the corpus callosum and cerebral white matter. Fifteen months ago, he visited the pediatrics department due to dysphagia, dysarthria, facial paralysis, and muscle weakness. Brain MRI revealed lesions similar to those observed here, and nerve conduction study revealed demyelinating neuropathy. He was treated with intravenous immunoglobulin (IVIg) and intravenous methylprednisolone, and his symptoms disappeared within a few days and Brain MRI 5 weeks after treatment revealed that the lesions had disappeared. Three months ago, while walking, the patient developed a knee strain, which was thought to be a recurrence of the immune-mediated neuropathy. His subjective symptom disappeared after administration of IVIg. The patient was diagnosed with X-linked Charcot-Marie-Tooth disease (CMTX1) based on genetic testing, which revealed a pathological variant of GJB1, c.124A>T (p.Ser42Cys). Peripheral neuropathy in CMTX1 may present with fluctuating symptoms and can be responsive to IVIg treatment. Recurrent brain lesions should also be considered in the diagnosis of CMTX1.

X-linked Charcot-Marie-Tooth disease type 1 (CMTX1) is a hereditary neuropathy caused by mutations in the GJB1 gene encoding Connexin 32 (Cx32). Despite its X-linked dominant inheritance, it has been suggested that the variable phenotypic expression of the disease in females may be due to skewed X chromosome inactivation (XCI) in Schwann cells. This pilot study aimed to examine the XCI patterns in archived sural nerve biopsies of female patients diagnosed with CMTX1 for the first time in the literature. Two unrelated female CMTX1 patients, initially misdiagnosed with chronic inflammatory demyelinating polyneuropathy (CIDP), with motor conduction blocks were included. GJB1 mutations were identified using whole-exome sequencing (WES). XCI patterns were analyzed using the human androgen receptor (HUMARA) assay on archived fresh-frozen sural nerve biopsy samples performed prior the genetic diagnosis and compared with age-matched vasculitic neuropathy controls. The GJB1 c.379 A > C mutation was identified in both CMTX1 patients. XCI analysis revealed a random XCI pattern in affected nerve tissues, with no significant differences between patients and controls. Contrary to previous hypotheses, our findings suggest that XCI does not contribute to phenotypic variability in female CMTX1 patients. These results highlight the complexity of CMTX1 pathophysiology and highlight the need for further studies on alternative mechanisms regulating disease severity in females.

X-linked Charcot-Marie-Tooth disease type 1 (CMTX1) ranks as the second most prevalent hereditary neuropathy and, currently, has no definitive cure. Emerging preclinical trials offer hope for potential clinical studies in the near future. While it is widely accepted that experimental groups in these trials should be balanced for age and gender, there is a current shortfall in data regarding phenotype-genotype correlations. Our aim was to provide a more detailed understanding of these correlations to facilitate the formation of well-matched patient groups in upcoming clinical trials. We conducted a retrospective evaluation of CMTX1 patients from 13 designated reference centers in France. Data on genetics, clinical features, and nerve conduction were systematically gathered. We analyzed the genotype-phenotype correlations in 275 CMTX1 patients belonging to 162 families and carrying 87 distinct variants. Patients with variants affecting the transmembrane domains demonstrated significantly greater severity, as evidenced by a Charcot-Marie-Tooth Examination Score of 10.5, compared to 7.1 for those with intracellular domain variants and 8.7 for extracellular domain variants (p < 0.000). These patients also experienced an earlier age of onset, showed slower ulnar nerve conduction velocities and had more substantial loss of motor amplitude. This study confirms the presence of a correlation between the mutated protein domain and the clinical phenotype. Patients with a variant in the transmembrane domains demonstrated a more severe clinical and electrophysiological profile. Consequently, the genotype could play a prognostic role in addition to its diagnostic role, and it will be essential to consider this in future clinical trials.

X-linked Charcot-Marie-Tooth disease Type 1 (CMTX1), caused by gap junction beta-1 (GJB1) mutations, is the second most common form of CMT. Patients present with length-dependent sensorimotor polyneuropathy and split hand syndrome. Males are more severely affected; females show variable symptoms because of skewed X-inactivation. This study reclassifies a GJB1 variant of uncertain significance as pathogenic using American College of Medical Genetics criteria. A family with neurologic symptoms underwent clinical evaluation, electrodiagnostic studies, genetic testing, and imaging. Affected individuals exhibited a sensorimotor polyneuropathy in an X-linked inheritance pattern with males having earlier, more severe symptoms. Characteristic findings included split hand syndrome and the suggestion of stroke-like episodes. Genetic testing revealed a GJB1 c.841T>C p.(Ser281Pro) variant. Analysis met American College of Medical Genetics criteria (1 strong, 3 moderate, 1 supporting) for pathogenicity. The Ser281Pro GJB1 variant meets pathogenic criteria for CMTX1, extending known pathogenic regions beyond the C-terminal Arg220 codon.