Clinical practice guidelines for the diagnosis and management of Charcot-Marie-Tooth disease

INTRODUCTION

Charcot-Marie-Tooth (CMT) disease is classified considering the neurophysiological and histological findings, the inheritance pattern and the underlying genetic defect. In recent years, with the advent of next generation sequencing, genetic complexity has increased exponentially, expanding the knowledge about disease pathways, and having an impact in clinical management. The aim of this guide is to offer recommendations for the diagnosis, prognosis, monitoring and treatment of this disease in Spain.

MATERIAL AND METHODS

This consensus guideline has been developed by a multidisciplinary panel encompassing a broad group of professionals including neurologists, neuropediatricians, geneticists, rehabilitators, and orthopaedic surgeons.

RECOMMENDATIONS

The diagnosis is based in the clinical characterization, usually presenting with a common phenotype. It should be followed by an appropriate neurophysiological study that allows for a correct classification, specific recommendations are established for the parameters that should be included. Genetic diagnosis must be approached in sequentially, once the PMP22 duplication has been ruled out if appropriate, a next generation sequencing should be considered taking into account the limitations of the available techniques. To date, there is no pharmacological treatment that modifies the course of the disease, but symptomatic management is important, as are the rehabilitation and orthopaedic considerations. The latter should be initiated early to identify and improve the patient's functional impairments, including individualised exercise guidelines, orthotic adaptation, and assessment of conservative surgeries such as tendon transpositions. The follow-up of patients with CMT is exclusively clinical, ancillary testing are not necessary in routine clinical practice.

Phenotypic, molecular, and functional characterization of COQ7-related primary CoQ10 deficiency: Hypomorphic variants and two distinct disease entities

Primary coenzyme Q10 (CoQ10) deficiency is a group of inborn errors of metabolism caused by defects in CoQ10 biosynthesis. Biallelic pathogenic variants in COQ7, encoding mitochondrial 5-demethoxyubiquinone hydroxylase, have been reported in nine patients from seven families. We identified five new patients with COQ7-related primary CoQ10 deficiency, performed clinical assessment of the patients, and studied the functional effects of current and previously reported COQ7 variants and potential treatment options. The main clinical features included a neonatal-onset presentation with severe neuromuscular, cardiorespiratory and renal involvement and a late-onset disease presenting with progressive neuropathy, lower extremity weakness, abnormal gait, and variable developmental delay. Baker's yeast orthologue of COQ7, CAT5, is required for growth on oxidative carbon sources and cat5Δ strain demonstrates oxidative growth defect. Expression of wild-type CAT5 could completely rescue the defect; however, yeast CAT5 harboring equivalent human pathogenic variants could not. Interestingly, cat5Δ yeast harboring p.Arg57Gln (equivalent to human p.Arg54Gln), p.Arg112Trp (equivalent to p.Arg107Trp), p.Ile69Asn (equivalent to p.Ile66Asn) and combination of p.Lys108Met and p.Leu116Pro (equivalent to the complex allele p.[Thr103Met;Leu111Pro]) partially rescued the growth defects, indicating these variants are hypomorphic alleles. Supplementation with 2,4 dihydroxybenzoic acid (2,4-diHB) rescued the growth defect of both the leaky and severe mutants. Overexpression of COQ8 and 2,4-diHB supplementation synergistically restored oxidative growth and respiratory defect. Overall, we define two distinct disease presentations of COQ7-related disorder with emerging genotype-phenotype correlation and validate the use of the yeast model for functional studies of COQ7 variants.

Spectrum of SPTLC1-related disorders: a novel case of 'Ser331 syndrome' that expand the phenotype of hereditary sensory and autonomic neuropathy type 1A and motor neuron diseases

We report a patient with early-onset hereditary sensory and autonomic neuropathy type 1A (HSAN-1A) who developed a distinct phenotype, with tongue fasciculation and atrophy, due to a mutation at serine 331 in the SPTLC1 gene. HSAN-1A manifestation causing tongue fasciculation and atrophy have been rarely found. Our report adds to the growing evidence of the existence of an overlap between hereditary neuropathy and motor neuron disease caused by pathogenic p.S331Y variant in SPTLC1 gene.

Nerve Sonography in Charcot-Marie-Tooth Disease: A Systematic Review and Meta-analysis of 6061 Measured Nerves

Because of the insidious character and variations in presenting symptoms, Charcot-Marie-Tooth (CMT) disease is challenging to diagnose in children. Diagnosis is based on clinical and nerve conduction studies, as well as genetic examination. Therefore, competent nerve imaging techniques and non-invasive alternatives to nerve conduction studies are a necessity, especially in children. We performed a systematic review and meta-analysis to evaluate the current evidence and effectiveness of ultrasound in investigating nerve cross-sectional area (CSA) in those with CMT compared with healthy controls and to pool the CSA measurements. We included studies published in international peer-reviewed journals that measured nerve CSA by ultrasound in patients with CMT. We implemented double-arm meta-analyses to compare the mean CSA of nerves between patients with CMT and healthy controls by calculating the pooled mean difference in CSA. Moreover, we performed subgroup analyses by stratifying the studies according to the site of CSA measurement and examined the difference in nerve CSA between CMT1A and other CMT types. The included studies provide measurements of 12 nerve roots and nerves (vagus, C3, C4, C5, C6, greater auricular, phrenic, median, ulnar, fibular, tibial and sural nerves) in 628 patients with CMT and 586 healthy controls with a total of 6061 measured nerves. Meta-analyses of sonographic nerve CSA are provided to express nerve ultrasonography in the diagnosis of CMT patient.

Clinical and neurophysiological findings in patients with hereditary neuropathy with liability to pressure palsy and chromosome 17p11.2 deletion

INTRODUCTION

Hereditary neuropathy with liability to pressure palsy (HNPP) is an autosomal dominant disorder, typically presenting with recurrent episodes of mononeuropathy in nerves susceptible to compression, with similar neurophysiological characteristics. However, other clinical and neurophysiological presentations have been reported.

METHODS

We retrospectively analysed the clinical and neurophysiological characteristics of 20 patients with genetically confirmed HNPP. Sixteen patients were studied in our department between 1996 and 2016.

RESULTS

In addition to the typical characteristics of HNPP, we found atypical forms including recurrent positional sensory symptoms in 3 patients, chronic sensorimotor polyneuropathy in one, and non-progressive mononeuropathy in one. Onset was early in 2 patients: one at the age of 7 years, with common peroneal nerve injury, and another at birth, with brachial plexus involvement. By frequency, the main pathological findings in the nerve conduction study were: decreased sensory nerve conduction velocity in the sural (84%) and the median and superficial peroneal nerves (94%); decreased motor nerve conduction velocity in the ulnar nerve through the elbow (97%), and increased motor distal latency of the median and deep peroneal nerves (74%).

CONCLUSION

Our results confirm the clinical variability of HNPP, with the most frequent nerve conduction study findings being the generalised decrease in sensory nerve conduction velocity, in addition to motor involvement, mainly in locations susceptible to nerve compression. The nerve conduction study can detect typical, atypical, and asymptomatic cases of HNPP.

Clinical and neurophysiological findings in patients with hereditary neuropathy with liability to pressure palsy and chromosome 17p11.2 deletion

INTRODUCTION

Hereditary neuropathy with liability to pressure palsy (HNPP) is an autosomal dominant disorder, typically presenting with recurrent episodes of mononeuropathy in nerves susceptible to compression, with similar neurophysiological characteristics. However, other clinical and neurophysiological presentations have been reported.

METHODS

We retrospectively analysed the clinical and neurophysiological characteristics of 20 patients with genetically confirmed HNPP. Sixteen patients were studied in our department between 1996 and 2016.

RESULTS

In addition to the typical characteristics of HNPP, we found atypical forms including recurrent positional sensory symptoms in 3 patients, chronic sensorimotor polyneuropathy in one, and non-progressive mononeuropathy in one. Onset was early in 2 patients: one at the age of 7 years, with common peroneal nerve injury, and another at birth, with brachial plexus involvement. By frequency, the main pathological findings in the nerve conduction study were: decreased sensory nerve conduction velocity in the sural (84%) and the median and superficial peroneal nerves (94%); decreased motor nerve conduction velocity in the ulnar nerve through the elbow (97%), and increased motor distal latency of the median and deep peroneal nerves (74%).

CONCLUSION

Our results confirm the clinical variability of HNPP, with the most frequent nerve conduction study findings being the generalised decrease in sensory nerve conduction velocity, in addition to motor involvement, mainly in locations susceptible to nerve compression. The nerve conduction study can detect typical, atypical, and asymptomatic cases of HNPP.

Association of SORD mutation with autosomal recessive asymmetric distal hereditary motor neuropathy

Background

The aim of this study was to identify the underlying genetic defect in a family segregating autosomal recessive asymmetric hereditary motor neuropathy (HMN). Asymmetric HMN has not been associated earlier with SORD mutations.

Methods

For this study, we have recruited a family and collected blood samples from affected and normal individuals of a family. Detailed clinical examination and electrophysiological studies were carried out. Whole exome sequencing was performed to detect the underlying genetic defect in this family. The potential variant was validated using the Sanger sequencing approach.

Results

Clinical and electrophysiological examination revealed asymmetric motor neuropathy with normal nerve conduction velocities and action potentials. Genetic analysis identified a homozygous mononucleotide deletion mutation (c.757delG) in a SORD gene in a patient. This mutation is predicted to cause premature truncation of a protein (p.A253Qfs*27).

Conclusions

Interestingly, the patient with homozygous SORD mutation demonstrates normal motor and nerve conduction velocities and action potentials. The affected individual describes in this study has a unique presentation of asymmetric motor neuropathy predominantly affecting the right side more than the left as supported by the clinical examination. This is the first report of SORD mutation from Saudi Arabia and this study further expands the phenotypic spectrum of SORD mutation.

Charcot-Marie-Tooth disease type 4C associated with myasthenia gravis: coincidental or a foreseeable association?

We reported one patient with Charcot-Marie-Tooth type 4C (CMT4C) who developed seropositive myasthenia gravis. Neuromuscular junction alterations in CMT4C patients have not yet been reported. However, few patients have been reported to simultaneously have MG and CMT, but none with CMT4C. Our report suggests that additional research is required to confirm whether genetic neuropathies may predispose to MG.

The impact of symptoms on daily life as perceived by patients with Charcot-Marie-Tooth type 1A disease

Introduction

In Charcot-Marie-Tooth type 1A (CMT1A) patients, daily life is mainly influenced by mobility and ambulation dysfunctions. The aim of our work was to evaluate the perception of disturbances that mostly impact on daily life in CMT1A patients and its difference on the basis of age, gender, disability, and quality of life.

Methods

Forty-one CMT1A patients underwent neurological assessment focused on establishing clinical disability through the Charcot-Marie-Tooth Neuropathy Score (CMTNS) and quality of life through the Short Form-36 (SF-36) questionnaire. We identified from CMT disturbances 5 categories [weakness in lower limbs (WLL), weakness in upper limbs (WUL), skeletal deformities (SD), sensory symptoms (SS), balance (B)] and patients classified the categories from the highest to the lowest impact on daily life (1: highest; 5: lowest). Ranking of the 5 categories, in the overall sample and in the different subgroups (dividing by gender, median of age and disease duration, CMTNS, domains of SF-36), was obtained and differences among subgroups were assessed using a bootstrap approach.

Results

Rank analysis showed that WLL was the most important disturbance on daily life whereas WUL had the lowest impact. In the older CMT1A group, the most important disturbance on daily life was B that was also the most relevant disturbance in patients with a greater disability. SD influenced daily life in younger patients. SS had less impact on daily life, with the exception of patients with a milder disability.

Discussion

Our findings demonstrated that the perception of disturbances that mostly impact on CMT1A patients’ daily life changes over the lifetime and with degree of disability.

Location matters - Genotype-phenotype correlation in LRSAM1 mutations associated with rare Charcot-Marie-Tooth neuropathy CMT2P

More than 80 genes are known to be associated with Charcot-Marie-Tooth disease (CMT). Mutations of LRSAM1 were identified as a rare cause and define the subgroup of axonal neuropathy CMT2P. We identified additional 14 patients out of 12 families. Clinical and electrophysiological data confirm a late-onset axonal neuropathy with a predominance of sensorimotor impairment. The patients harbored ten different variants in LRSAM1, seven of which were novel. Due to variable inheritance patterns and clustering of pathogenic variants in 3´-prime exons, interpretation of genetic variants in LRSAM1 is challenging. The majority follows dominant inheritance, whereas recessive inheritance has been described for one variant. Variants at the 3`end may or may not escape from nonsense-mediated decay, thereby defining the pattern of inheritance. Our data emphasize the importance of the C-terminal RING domain, which exerts a dominant-negative effect on protein function, whenever affected by an altered or truncated protein. In conclusion, CMT2P is a rare, but nevertheless relevant cause of adult-onset axonal and painful neuropathy. ACMG (American College of Medical Genetics and genomics) criteria should be carefully applied in variant interpretation, with special attention to premature termination codon-introducing variants and their location within the gene.

Current and future applications of ultrasound imaging in peripheral nerve disorders

Neuromuscular ultrasound (NMUS) is a rapidly evolving technique used in neuromuscular medicine to provide complimentary information to standard electrodiagnostic studies. NMUS provides a dynamic, real time assessment of anatomy which can alter both diagnostic and management pathways in peripheral nerve disorders. This review describes the current and future techniques used in NMUS and details the applications and developments in the diagnosis and monitoring of compressive, hereditary, immune-mediated and axonal peripheral nerve disorders, and motor neuron diseases. Technological advances have allowed the increased utilisation of ultrasound for management of peripheral nerve disorders; however, several practical considerations need to be taken into account to facilitate the widespread uptake of this technique.

Novel MTMR2 mutation causing severe Charcot-Marie-Tooth type 4B1 disease: a case report

Mutations in myotubularin-related protein 2 (MTMR2) were shown to underlie Charcot-Marie-Tooth type 4B1 (CMT4B1) disease, a rare autosomal recessive demyelinating neuropathy, characterized by severe early-onset motor and sensory neuropathy. We describe three siblings of consanguineous kindred presenting with hypotonia, reduced muscle tone, action tremor, dysmetria, areflexia, and skeletal deformities, consistent with a diagnosis of CMT. Whole-exome sequencing identified a novel homozygous c.336_337 insertion mutation in MTMR2, resulting in a frameshift and putative truncated protein. In this concise report, we discuss the clinical presentation of this rare disease and support the limited number of observations regarding the pathogenesis of MTMR2-related neuropathies.

Disorders of mitochondrial dynamics in peripheral neuropathy: Clues from hereditary neuropathy and diabetes

Peripheral neuropathy is a common and debilitating complication of diabetes and prediabetes. Recent clinical studies have identified an association between the development of neuropathy and dyslipidemia in prediabetic and diabetic patients. Despite the prevalence of this complication, studies identifying molecular mechanisms that underlie neuropathy progression in prediabetes or diabetes are limited. However, dysfunctional mitochondrial pathways in hereditary neuropathy provide feasible molecular targets for assessing mitochondrial dysfunction in neuropathy associated with prediabetes or diabetes. Recent studies suggest that elevated levels of dietary saturated fatty acids (SFAs) associated with dyslipidemia impair mitochondrial dynamics in sensory neurons by inducing mitochondrial depolarization, compromising mitochondrial bioenergetics, and impairing axonal mitochondrial transport. This causes lower neuronal ATP and apoptosis. Conversely, monounsaturated fatty acids (MUFAs) restore nerve and sensory mitochondrial function. Understanding the mitochondrial pathways that contribute to neuropathy progression in prediabetes and diabetes may provide therapeutic targets for the treatment of this debilitating complication.

Novel mutations in HINT1 gene cause autosomal recessive axonal neuropathy with neuromyotonia in two cases of sensorimotor neuropathy and one case of motor neuropathy

Autosomal recessive axonal neuropathy with neuromyotonia (ARANNM) is a rare disease caused by mutations of histidine triad nucleotide binding protein 1 (HINT1) gene. ARANNM has been reported mainly in European countries but little reported so far in China. We describe novel mutations of HINT1 in three Chinese patients with ARANNM from unrelated families. Patient 1 was a 14-year-old girl who presented with progressive distal weakness of upper limbs at two years of age. After that, she reported weakness of both feet, and difficulty in muscle relaxation after making a fist. Patient 2 was an 18-year-old boy, who presented with progressive distal weakness of all limbs with foot drop at the age of ten with loss of ambulation at age 15. Patient 3 was a 26-year-old man who had been afflicted with weakness and atrophy of distal lower limbs since the age of 16 complaining about muscle stiffness of the lower limbs when standing and walking, and contraction of finger flexion muscles when releasing a forced grip. Electrodiagnostic testing revealed an axonal motor or sensorimotor neuropathy with or without myokymic discharges. Sural biopsy showed no pathological changes in patient 1 and mild axonal neuropathies with demyelination in patients 2 and 3. Genetic analysis revealed HINT1 with novel compound heterozygous c.112T > C (p.C38R) and c.171G > C (p.K57N) mutations in patient 1, homozygous c.112T > C (p.C38R) mutation in patient 2, as well as compound heterozygous c.112T > C (p.C38R) and c.98T > C (p.F33S) mutations in patient 3. Our study, for the first time, confirms ARANNM in the Chinese population. These genetic findings can help expand the genotypic spectrum of HINT1 mutations.

Gabrielle Lévy and the Roussy-Lévy syndrome

In 1934, Gabrielle Lévy died at the age of 48. She became well known for an article she published on a hereditary polyneuropathy in cooperation with Gustav Roussy, resulting in the eponym Roussy-Lévy syndrome. Not much is known about this extraordinary neurologist/neuropathologist. Her family declared that she died from the disease she was studying. She was a pupil of Pierre Marie, with whom she worked at the Salpêtrière in Paris and wrote on war neurology. In cooperation with Marie, she published a number of articles on postencephalitic syndromes, which also became the subject of her 1922 thesis. Three years later, she became associate physician at the Paul-Brousse Hospital in Paris, where the study of brain tumors became one of the subjects of her scientific work. Remarkably, Lévy was first author in a few of her many articles, although Roussy confirmed that she often initiated the study and even wrote the main part. In this article her career is considered in the context of the struggle of women physicians to improve their position during the early-twentieth century. She probably died from a brain tumor or a postencephalitic syndrome.

Genotypic and phenotypic spectrum of the most common causative genes of Charcot-Marie-Tooth disease in Hungarian patients

Charcot-Marie-Tooth neuropathy (CMT) is a genetically and clinically heterogeneous group of neuromuscular disorders with an overall prevalence of 1 per 2500. Here we report the first comprehensive genetic epidemiology study of Hungarian CMT patients. 409 CMT1 and 122 CMT2 patients were enrolled and genetic testing of PMP22, GJB1, MPZ, EGR2 and MFN2 genes were performed routinely. NDRG1 and CTDP1 genes were screened only for founder mutations in Roma patients. Causative genetic mutations were identified in 67.2% of the CMT1 and in 33.6% of the CMT2 cases, which indicates an overall success rate of 59.9% in the study population. Considering all affected individuals, alterations were most frequently found in PMP22 (40.5%), followed by GJB1 (9.2%), MPZ (4.5%), MFN2 (2.5%), NDRG1 (1.5%), EGR2 (0.8%) and CTDP1 (0.8%). The phenotypic spectrum and the disease severity of the studied patients also varied broadly. Deafness and autoimmune disorders were more often associated with PMP22 duplication, while MFN2 and GJB1 mutations were frequently present with central nervous system abnormalities. Our study may be helpful in determining the strategy of genetic diagnostics in Hungarian CMT patients.

Phenotypical features of a new dominant GDAP1 pathogenic variant (p.R226del) in axonal Charcot-Marie-Tooth disease

There are few reports on axonal CMT due to dominant GDAP1 mutations. We describe two unrelated Spanish families with a dominant axonal CMT. A novel in frame GAA deletion in exon 5 of the GDAP1 gene (c.677_679del; p.R226del) was identified in both families. Disease onset varied from early childhood to adulthood. Affected family members complained of distal lower limb weakness, cramps and foot deformities with variable CMTNS score in both families. Several individuals were asymptomatic or had paraesthesia only, however neurological examination and nerve conduction studies demonstrated neuropathic signs. Transfection of HeLa cells with the p.R226del mutation led to an increased mitochondrial aggregation. We report an AD-CMT2K with large phenotypic variability due to a novel dominant GDAP1 variant. This is the second founder GDAP1 pathogenic variant reported in Spain.

The modified ultrasound pattern sum score mUPSS as additional diagnostic tool for genetically distinct hereditary neuropathies

The objective of this study is to evaluate the nerve ultrasound characteristics in genetically distinct inherited neuropathies, the value of the modified ultrasound pattern sum score (mUPSS) to differentiate between the subtypes and the correlation of ultrasound with nerve conduction studies (NCS), disease duration and severity. All patients underwent a standardized neurological examination, ultrasound, and NCS. In addition, genetic testing was performed. Consequently, mUPSS was applied, which is a sum-score of cross-sectional areas (CSA) at predefined anatomical points in different nerves. 31 patients were included (10xCharcot-Marie-Tooth (CMT)1a, 3xCMT1b, 3xCMTX, 9xCMT2, 6xHNPP [Hereditary neuropathy with liability to pressure palsies]). Generalized, homogeneous nerve enlargement and significantly increased UPS scores emphasized the diagnosis of demyelinating neuropathy, particularly CMT1a and CMT1b. The amount of enlargement did not depend on disease duration, symptom severity, height and weight. In CMTX the nerves were enlarged, as well, however, only in the roots and lower limbs, most prominent in men. In CMT2 no significant enlargement was detectable. In HNPP the CSA values were increased at entrapped sites, and not elsewhere. However, a distinction from CMT1, which also showed enlarged CSA values at entrapment sites, was only possible by calculating the entrapment ratios and entrapment score. The mUPSS allowed distinction between CMT1a (increased UPS scores, entrapment ratios <1.0) and HNPP (low UPS scores, entrapment ratios >1.4), while CMT1b and CMTX showed intermediate UPS types and entrapment ratios <1.0. Although based on few cases, ultrasound revealed consistent and homogeneous nerve alteration in certain inherited neuropathies. The modified UPSS is a quantitative tool, which may provide useful information for diagnosis, differentiation and follow-up evaluation in addition to NCS and molecular testing.

A cohort study of Han Chinese MFN2-related Charcot-Marie-Tooth 2A

BACKGROUND

Charcot-Marie-Tooth 2A (CMT2A) is caused by mutations in mitochondrial fusion protein mitofusin 2 (MFN2). CMT2A had a large variety of clinical symptoms and several cohort studies were published recently. This study is to summarized the clinical, electrophysiological, pathological and genetic features in Han Chinese CMT2A.

METHODS

20 patients from 12 unrelated Chinese families with MFN2 related CMT2A were collected. Clinical symptom, nerve conduction velocity study, sural nerve pathology and MFN2 gene mutation were retrospectively analyzed.

RESULTS

We confirmed MFN2 gene mutation in 12 indexes. Nineteen of 20 (95%) patients were classified as early onset phenotypes of CMT2A, including four cases (20%) with infantile onset. Motor nerve conduction velocity (MNCV) of median nerve was above 38m/s in 50% of patients and not recordable in remaining patients. MNCV was not affected by onset age, disease course and mutation site in different patients and MNCV had no correlation with severity of symptoms. Sural nerve biopsy revealed mixed axonal and demyelination change. Loss of myelinated fibers and atypical onions was found in all cases. Electron microscopic (EM) examination of sural nerve confirmed mitochondrial vacuation and aggregation both in myelinated and unmyelinated axons. Eight mutations were detected in 12 indexes, including two novel mutations. The amino acid residue at position 94 of MFN2 protein was a hot spot in Han Chinese patients, followed by R104W.

CONCLUSIONS

Eraly onset, even infantile onset was more common in our Chinese population. MNCV of median nerve could be either above 38m/s or unrecordable in CMT2A. Pathologically, mixed axon and myelin change should be considered since onion change was frequently observed in most CMT2A.

Hereditary Neuropathy with Liability to Pressure Palsy Presenting as an Acute Brachial Plexopathy: A Lover's Palsy

It is generally regarded that patients with hereditary neuropathy to pressure palsies, due to a deletion in the PMP22 gene, show recurrent pressure palsy and generalised peripheral neuropathy (pes cavus and hammer toes sometimes develop). Brachial plexopathy is rarely identified as a first presentation of hereditary neuropathy to pressure palsies. We describe a young man who developed a painless flail upper limb with a clinical diagnosis of a brachial plexopathy after his partner slept on his arm – a PMP22 deletion was found. His father, who had a symmetrical polyneuropathy without recurrent mononeuropathies, shared the PMP22 deletion.

[Review of the recent literature on hereditary neuropathies]

The recent literature included interesting reports on the pathogenic mechanisms of hereditary neuropathies. The axonal traffic and its abnormalities in some forms of Charcot-Marie-Tooth (CMT) disease were particularly reviewed by Bucci et al. Many genes related to CMT disease code for proteins that are involved directly or not in intracellular traffic. KIF1B controls vesicle motility on microtubules. MTMR2, MTMR13 and FIG4 regulate the metabolism of phosphoinositide at the level of endosomes. The HSPs are involved in the proteasomal degradation. GDAP1 and MFN2 regulate the mitochondrial fission and fusion respectively and the mitochondial transport within the axon. Pareyson et al. reported a review on peripheral neuropathies in mitochondrial disorders. They used the term of "mitochondrial CMT" for the forms of CMT with abnormal mitochondrial dynamic or structure. Among the new entities, we can draw the attention to a proximal form of hereditary motor and sensory neuropathy with autosomal dominant inheritance, which is characterized by motor deficit with cramps and fasciculations predominating in proximal muscles. Distal sensory deficit can be present. The gene TFG on chromosome 3 has been recently identified to be responsible for this form. Another rare form of axonal autosomal recessive neuropathy due to HNT1 gene mutation is characterized by the presence of hands myotonia that appears later than neuropathy but constitute an interesting clinical hallmark to orientate the diagnosis of this form. In terms of differential diagnosis, CMT4J due to FIG4 mutation can present with a rapidly progressive and asymmetric weakness that resembles CIDP. Bouhy et al. made an interesting review on the therapeutic trials, animal models and the future therapeutic strategies to be developed in CMT disease.

Clinical spectrum and gender differences in a large cohort of Charcot-Marie-Tooth type 1A patients

INTRODUCTION

Heterogeneous clinical presentation and gender differences were reported in Charcot-Marie-Tooth disease type 1A (CMT1A).

METHODS

This report examined demographic and clinical data collected during a randomised controlled trial, to describe the clinical spectrum of a large and well-defined cohort of CMT1A patients.

RESULTS

Among the 189 symptomatic patients screened, three patients (1.6%) reported first symptoms in the upper limbs, which may be misleading when establishing the clinical diagnosis. The quality of life (QoL) of patients was significantly deteriorated compared to the standard population, and slightly better compared to multiple sclerosis patients. According to the literature, patients reported several disorders which may be associated with CMT1A, including auditory dysfunction (7.9%), Carpal Tunnel Syndrome (CTS) (7.9%) or sleep apnoea (4.2%). Compared to available data, we reported more patients with CTS and fewer patients with sleep apnoea. Women were more affected by CTS than men (11% and 2.8%, respectively). Women also reported an earlier onset of symptoms than men (8.6±9.5 years and 13.1±14 years, respectively), higher deterioration of their QoL and higher disability of their upper limb, assessed by Overall Neuropathy Limitation Scale (p=0.023).

CONCLUSIONS

This information will be useful for better understanding of this disease and for designing future clinical studies.

Charcot-Marie-Tooth disease: frequency of genetic subtypes in a German neuromuscular center population

Charcot-Marie-Tooth (CMT) neuropathies belong to the most common neurogenetic disorders. To date, mutations in more than 40 genes are known to be able to cause CMT. This genetic heterogeneity is a challenge for genetic diagnostics. Data on frequencies of mutations in CMT genes from large patient cohorts are needed to develop strategies for efficient genetic testing. In this study we have analysed patient histories, electrophysiological and genetic testing data in our cohort of 776 patients. In electrophysiologically demyelinating CMT, PMP22 duplication was the most common genetic cause, followed by mutations in GJB1 and MPZ. In axonal CMT, GJB1 was the most commonly affected gene, followed by MFN2 and MPZ. In CMT1, the clearance rate was 66%, in CMT2 it was 35%. Overall, the genetic clearance rate in our patient cohort was 58%. We found a higher rate of genetic diagnosis in patients seen in our neuromuscular center compared to out-of-clinic patients whose DNA was tested in our laboratory. This study provides further data on frequencies of CMT genes and subtypes and points to the importance of a thorough clinical and electrophysiological work-up for the direction of genetic testing.

The first Japanese case of Charcot-Marie-Tooth disease type 4H with a novel FGD4 c.837-1G>A mutation

Charcot-Marie-Tooth disease type 4H (CMT4H) is an autosomal recessive demyelinating neuropathy. It presents as infancy or early childhood-onset neuropathy associated with FGD4 mutations. Clinically it causes predominantly distal muscle weakness. On nerve biopsy examination, myelin outfoldings are seen. The previous case reports have been from regions bordering the Mediterranean, as well as a family from Northern Ireland. This paper presents the detailed clinical course of the first reported case of CMT4H in a Japanese woman. The patient showed mild weakness without scoliosis and a severe sensory disturbance; her functional impairment was less severe than the previously published cases. In addition, a novel homozygous FGD4 c.837-1G>A mutation was identified in this patient.

Peripheral neuropathy: clinical and electrophysiological considerations

This article is a primer on the pathophysiology and clinical evaluation of peripheral neuropathy for the radiologist. Magnetic resonance neurography has utility in the diagnosis of many focal peripheral nerve lesions. When combined with history, examination, electrophysiology, and laboratory data, future advancements in high-field magnetic resonance neurography may play an increasingly important role in the evaluation of patients with peripheral neuropathy.

Hypertelorism in Charcot-Marie-Tooth disease 1A from the common PMP22 duplication: A Case Report

The 1.4Mb tandem-duplication in the PMP22 gene at 17p11.2 usually manifests as hereditary sensorimotor polyneuropathy with foot deformity, sensorineural hearing-loss, moderate developmental delay, and gait disturbance. Hypertelorism and marked phenotypic variability within a single family has not been reported. In a single family, the PMP22 tandem-duplication manifested as short stature, sensorimotor polyneuropathy, tremor, ataxia, sensorineural hearing-loss, and hypothyroidism in the 27 years-old index case, as mild facial dysmorphism, muscle cramps, tinnitus, intention tremor, bradydiadochokinesia, and sensorimotor polyneuropathy in the 31 year-old half-brother of the index-patient, and as sensorimotor polyneuropathy and foot-deformity in the father of the two. The half-brother additionally presented with hypertelorism, not previously reported in PMP22 tandem-duplication carriers. The presented cases show that the tandem-duplication 17p11.2 may present with marked intra-familial phenotype variability and that mild facial dysmorphism with stuck-out ears and hypertelorism may be a rare phenotypic feature of this mutation. The causal relation between facial dysmorphism and the PMP22 tandem-duplication, however, remains speculative.

Overlapping molecular pathological themes link Charcot-Marie-Tooth neuropathies and hereditary spastic paraplegias

In this review we focus on Charcot-Marie-Tooth (CMT) neuropathies and hereditary spastic paraplegias (HSPs). Although these diseases differ in whether they primarily affect the peripheral or central nervous system, both are genetically determined, progressive, long axonopathies that affect motor and sensory pathways. This commonality suggests that there might be similarities in the molecular pathology underlying these conditions, and here we compare the molecular genetics and cellular pathology of the two groups.

Superior mesenteric artery syndrome in a patient with Charcot Marie Tooth disease

The extrinsic compression of the third part of the duodenum as it passes through the aorto-mesenteric angle is known as the superior mesenteric artery syndrome (SMAS). This syndrome is a rare mechanical cause of upper intestinal obstruction, with a reported incidence of between 0.2% and 0.78%. Clinical manifestations of SMAS may be chronic or acute; chronic symptoms include intermittent gastric pain, fullness and occasional episodes of postprandial vomiting, while acute symptoms include incoercible vomiting, oral intolerance, mainly epigastric abdominal distension and abdominal pain. Surgery is recommended only when initial conservative treatment fails. Here, we report what appears to be the third published case of SMAS associated with hereditary motor and sensory neuropathy or Charcot Marie Tooth disease.