Treatment of Charcot-Marie-Tooth neuropathies

Case Report: Charcot-marie-tooth disease caused by a de novo MORC2 gene mutation - novel insights into pathogenicity and treatment

Charcot-Marie-Tooth disease (CMT) is a hereditary peripheral neuropathy involving approximately 80 pathogenic genes. Whole-exome sequencing (WES) and confirmatory Sanger sequencing analysis was applied to identify the disease-causing mutations in a Chinese patient with lower limb weakness. We present an 18-year-old male with a 2.5-year history of progressive lower limb weakness and an unsteady gait. Upon admission, a physical examination revealed hands tremulousness, bilateral calf muscle wasting and weakness, pes cavus, and elevated serum creatine kinase (CK) levels. Electromyography demonstrated axonal neuropathy affecting both upper and lower limbs. A de novo heterozygous missense mutation was identified in the MORC2 gene, NM_001303256.3: c.1199A>G, NP_001290186.1: p.Gln400Arg. Consequently, these clinical and genetic findings suggested a diagnosis of hereditary peripheral neuropathy, CMT type 2Z. Oral mecobalamin and coenzyme Q10 was initiated as subsequent treatment. Our study firstly reports the MORC2 c.1199A>G mutation occurring de novo, highlighting its causal association with CMT2Z, and prompting its reclassification as likely pathogenic. Oral mecobalamin and coenzyme Q10 might be a potential treatment approach for early-stage CMT2Z. We recommend genetic testing for CMT patients to identify the genetic etiology, thereby improving clinical management and facilitating genetic counseling.

Current Treatment Methods for Charcot-Marie-Tooth Diseases

Charcot-Marie-Tooth (CMT) disease, the most common inherited neuromuscular disorder, exhibits a wide phenotypic range, genetic heterogeneity, and a variable disease course. The diverse molecular genetic mechanisms of CMT were discovered over the past three decades with the development of molecular biology and gene sequencing technologies. These methods have brought new options for CMT reclassification and led to an exciting era of treatment target discovery for this incurable disease. Currently, there are no approved disease management methods that can fully cure patients with CMT, and rehabilitation, orthotics, and surgery are the only available treatments to ameliorate symptoms. Considerable research attention has been given to disease-modifying therapies, including gene silencing, gene addition, and gene editing, but most treatments that reach clinical trials are drug treatments, while currently, only gene therapies for CMT2S have reached the clinical trial stage. In this review, we highlight the pathogenic mechanisms and therapeutic investigations of different subtypes of CMT, and promising therapeutic approaches are also discussed.

Navigating the Landscape of CMT1B: Understanding Genetic Pathways, Disease Models, and Potential Therapeutic Approaches

Charcot-Marie-Tooth type 1B (CMT1B) is a peripheral neuropathy caused by mutations in the gene encoding myelin protein zero (MPZ), a key component of the myelin sheath in Schwann cells. Mutations in the MPZ gene can lead to protein misfolding, unfolded protein response (UPR), endoplasmic reticulum (ER) stress, or protein mistrafficking. Despite significant progress in understanding the disease mechanisms, there is currently no effective treatment for CMT1B, with therapeutic strategies primarily focused on supportive care. Gene therapy represents a promising therapeutic approach for treating CMT1B. To develop a treatment and better design preclinical studies, an in-depth understanding of the pathophysiological mechanisms and animal models is essential. In this review, we present a comprehensive overview of the disease mechanisms, preclinical models, and recent advancements in therapeutic research for CMT1B, while also addressing the existing challenges in the field. This review aims to deepen the understanding of CMT1B and to encourage further research towards the development of effective treatments for CMT1B patients.

A Case of Charcot-Marie-Tooth Disease Causing Colitis and Electrolyte Imbalances

Peripheral nerve injury is a result of the rare and crippling Charcot-Marie-Tooth (CMT) disease. Although it can happen at any age, progressive muscle weakening is most obvious in adolescence or the early stages of adulthood. We present a case of an 81-year-old female with recurrent urinary tract infections (UTIs), complaints of abdominal pain and constipation, as well as dysuria with abnormal electrolyte levels. This case serves as an effective symptomatic treatment plan for a patient with this rare neuromuscular disorder.

Identification of a Novel Homozygous Mutation in MTMR2 Gene Causes Very Rare Charcot-Marie-Tooth Disease Type 4B1

Background

Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of disorders involving peripheral nervous system. Charcot-Marie-Tooth disease 4B1 (CMT4B1) is a rare subtype of CMT. CMT4B1 is an axonal demyelinating polyneuropathy with an autosomal recessive mode of inheritance. Patients with CMT4B1 usually manifested with dysfunction of the motor and sensory systems which leads to gradual and progressive muscular weakness and atrophy, starting from the peroneal muscles and finally affecting the distal muscles. Germline mutations in MTMR2 gene causes CMT4B1.

Material and Methods

In this study, we investigated a 4-year-old Chinese boy with gradual and progressive weakness and atrophy of both proximal and distal muscles. The proband's parents did not show any abnormalities. Whole-exome sequencing and Sanger sequencing were performed.

Results

Whole-exome sequencing identified a novel homozygous nonsense mutation (c.118A>T; p.Lys40*) in exon 2 of MTMR2 gene in the proband. This novel mutation leads to the formation of a truncated MTMR2 protein of 39 amino acids instead of the wild- type MTMR2 protein of 643 amino acids. This mutation is predicted to cause the complete loss of the PH-GRAM domain, phosphatase domain, coiled-coil domain, and PDZ-binding motif of the MTMR2 protein. Sanger sequencing revealed that the proband's parents carried the mutation in a heterozygous state. This mutation was absent in 100 healthy control individuals.

Conclusion

This study reports the first mutation in MTMR2 associated with CMT4B1 in a Chinese population. Our study also showed the importance of whole-exome sequencing in identifying candidate genes and disease-causing variants in patients with CMT4B1.