The Charcot-Marie-Tooth syndrome: clinical aspects from a population study in South Wales, UK

A meta-analysis on the prevalence of Charcot-Marie-Tooth disease and related inherited peripheral neuropathies

BACKGROUND

Charcot-Marie-Tooth disease and related inherited peripheral neuropathies (CMT&RIPNs) brings great suffering and heavy burden to patients, but its global prevalence rates have not been well described.

METHODS

We searched major English and Chinese databases for studies reporting the prevalence of CMT&RIPNs from the establishment of the databases to September 26, 2022. Based on the age, gender, study design, study region, and disease subtype, the included studies were correspondingly synthesized for meta-analyses on the overall prevalence and/or the subgroup analyses by using pool arcsine transformed proportions in the random-effects model.

RESULTS

Of the finally included 31 studies, 21 studied the whole age population and various types of CMT&RIPNs, and the others reported specific disease subtype(s) or adult or non-adult populations. The pooled prevalence was 17.69/100,000 (95% CI 12.32-24.33) for the whole age population and significantly higher for CMT1 [10.61/100,000 (95% CI 7.06-14.64)] than for other subtypes (P' < 0.001). Without statistical significance, the prevalence seemed higher in those aged ≥ 16 or 18 years (21.02/100,000) than in those aged < 16 years (16.13/100,000), in males (22.50/100,000) than in females (17.95/100,000), and in Northern Europe (30.97/100,000) than in other regions.

CONCLUSION

CMT&RIPNs are relatively more prevalent as CMT1 in the disease subtypes, and probably prevalent in older ages, males, and Northern Europe. More studies on the epidemiological characteristics of CMT&RIPNs with well-defined diagnosis criteria are needed to improve the prevalence evaluation and to arouse more attention to health care support.

Pregnancy outcome in Charcot-Marie-Tooth disease: results of the CMT-NET cohort study in Germany

Background and purpose

Systematic research on the effect of Charcot–Marie–Tooth (CMT) disease on the outcome of pregnancy and conversely the effect of pregnancy on neuropathy is still sparse.

Methods

A clinical cohort study and cross‐sectional study within the German CMT‐NET was conducted between 2016 and 2019. Inclusion criteria were a confirmed diagnosis of CMT and at least one completed pregnancy after 1990. All participants agreed to fill in questionnaires and have their medical files reviewed.

Results

The study group comprised 54 women with a total of 98 pregnancies. The mean age at onset of CMT disease was 12.6 years (range 0–37 years). Fifty (92%) patients had autosomal dominant CMT; two patients each (4%) had X‐linked and autosomal recessive CMT. Forty patients (74%) had a PMP22 gene duplication (CMT1A). Obstetric complications did not differ significantly from a German reference population, neither in the whole group nor in the CMT1A group. Overall there was no increased newborn morbidity and mortality. About one‐third of patients reported exacerbation of CMT disease in or after pregnancy. No adverse effects of anaesthesia were reported. Most participants stressed a positive attitude and awareness of challenges associated with pregnancy. Important issues were assistance and support in caring for the family.

Discussion

In line with findings from our previous study undertaken in the 1990s, there were no increased complication rates for pregnancy and delivery. These results are reassuring for the vast majority of CMT patients and are important for family planning and clinical care.

Charcot-Marie-Tooth 2F (Hsp27 mutations): A review

Charcot-Marie-Tooth disease is a commonly inherited form of neuropathy. Although named over 100 years ago, identification of subtypes of Charcot-Marie-Tooth has rapidly expanded in the preceding decades with the advancement of genetic sequencing, including type 2F (CMT2F), due to mutations in heat shock protein 27 (Hsp27). However, despite CMT being one of the most common inherited neurological diseases, definitive mechanistic models of pathology and effective treatments for CMT2F are lacking. This review extensively profiles the published literature on CMT2F and distal hereditary motor neuropathy II (dHMN II), a similar neuropathy with exclusively motor symptoms that is also due to mutations in Hsp27. This includes a review of case reports and sequencing studies detailing disease course. Included are tables listing of all known published mutations of Hsp27 that cause symptoms of CMT2F and dHMN II. Furthermore, pathological mechanisms are assessed. While many groups have established pathologies relating to defective chaperone function, cellular neurofilament and microtubule structure and function, and mitochondrial and metabolic dysfunction, there are still discrepancies in results between different model systems. Moreover, initial mouse models have also produced promising results with similar phenotypes to humans, however discrepancies still exist. Both patient-focused and scientific studies have demonstrated variability in phenotypes even considering specific mutations. Given the clinical heterogeneity in presentation, CMT2F and dHMN II likely result from similar pathological mechanisms of the same general disease process that may present distinctly due to other genetic and environment influences. Determining how these influences exert their effects to produce pathology contributing to the disease phenotype will be a major future challenge ahead in the field.

Genetic epidemiology, demographic, and clinical characteristics of Charcot-Marie-tooth disease in the island of Gran Canaria (Spain)

Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuromuscular disorder. This study involves the entire known CMT patient registry in Gran Canaria, represented by 256 patients belonging to 79 unrelated families, who were clinically and genetically characterized, along with physical and neurophysiological evaluation on 181 and 165 patients, respectively. Complete genotyping showed an estimated prevalence of CMT disease of 30.08/100 000 (95% confidence interval [CI] = 26.5;33.9), corresponding mainly (78.5%) to CMT1A (23.6/100 000) and hereditary neuropathy with liability to pressure palsies [HNPP] 17.5%; 5.29/100 000). Most patients (198) with CMT1A carried the 17p11.2 duplication including the PMP22 gene, 45 patients with HNPP were all affected by deletion of the 17p11.2 locus, and 10 patients presented with axonal phenotypes: CMT2A (MFN2), CMT2N (AARS), and CMT1X (GJB1). Despite showing a classical CMT1A phenotype, we found a much earlier age of onset in our CMT1A patients, along with increased frequency of appearance of postural hand tremor. Bilateral tongue atrophy was an additional phenotype observed. Being this CMT1A group, one of the largest cohorts known to date, this study provided a unique opportunity to further define the clinical phenotype of CMT1A patients carrying the 17p11.2 duplication in a homogeneous ethnic group.

Decreased ceramide underlies mitochondrial dysfunction in Charcot-Marie-Tooth 2F

Charcot-Marie-Tooth (CMT) disease is the most commonly inherited neurologic disorder, but its molecular mechanisms remain unclear. One variant of CMT, 2F, is characterized by mutations in heat shock protein 27 (Hsp27). As bioactive sphingolipids have been implicated in neurodegenerative diseases, we sought to determine if their dysregulation is involved in CMT. Here, we show that Hsp27 knockout mice demonstrated decreases in ceramide in peripheral nerve tissue and that the disease-associated Hsp27 S135F mutant demonstrated decreases in mitochondrial ceramide. Given that Hsp27 is a chaperone protein, we examined its role in regulating ceramide synthases (CerSs), an enzyme family responsible for catalyzing generation of the sphingolipid ceramide. We determined that CerSs colocalized with Hsp27, and upon the presence of S135F mutants, CerS1 lost its colocalization with mitochondria suggesting that decreased mitochondrial ceramides result from reduced mitochondrial CerS localization rather than decreased CerS activity. Mitochondria in mutant cells appeared larger with increased interconnectivity. Furthermore, mutant cell lines demonstrated decreased mitochondrial respiratory function and increased autophagic flux. Mitochondrial structural and functional changes were recapitulated by blocking ceramide generation pharmacologically. These results suggest that mutant Hsp27 decreases mitochondrial ceramide levels, producing structural and functional changes in mitochondria leading to neuronal degeneration.-Schwartz, N. U., Linzer, R. W., Truman, J.-P., Gurevich, M., Hannun, Y. A., Senkal, C. E., Obeid, L. M. Decreased ceramide underlies mitochondrial dysfunction in Charcot-Marie-Tooth 2F.

Charcot-Marie-Tooth disease in Denmark: a nationwide register-based study of mortality, prevalence and incidence

OBJECTIVES

Charcot-Marie-Tooth disease (CMT) is the most common inherited disorder of the peripheral nervous system, yet no studies have compared the mortality in patients with CMT with that of the general population, and prevalence estimates vary considerably. We performed a nationwide register-based study to investigate the prevalence, incidence and mortality of CMT in Denmark.

DESIGN

We used the Danish National Patient Registry to select all records with primary diagnostic codes for CMT between 1977 and 2012 given at a neurological, neurophysiological, paediatric or clinical genetic clinic. The prevalence was estimated by 31 December 2012, and the incidence rate was calculated based on data from 1988 to 2012. We calculated a standardised mortality ratio (SMR) and an absolute excess mortality rate (AER) stratified according to age categories and disease duration.

RESULTS

A total of 1534 patients (652 women) were identified. The prevalence proportion was 22.5 per 100 000 (95% CI 21.2 to 23.7) and the incidence rate was 0.98 (95% CI 0.93 to 1.04) per 100 000 person-years. The SMR was 1.36 (95% CI 1.21 to 1.53), and the AER was 4.87 per 1000 person-years (95% CI 2.77 to 6.96). We found a significantly higher SMR in cases below 50 years of age, and in cases with disease duration of more than 10 years.

CONCLUSIONS

We found a reduced life expectancy among patients diagnosed with CMT. To our knowledge, this is the first study of CMT to use nationwide register-based data, and the first to report an SMR and an AER.

Molecular Epidemiology of Charcot-Marie-Tooth Disease in Northern Ostrobothnia, Finland: A Population-Based Study

BACKGROUND

Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuromuscular disorder with a population prevalence of 9.7-82.3/100,000. In this study, we have estimated the prevalence of CMT and its subtypes in Finland and examined the frequency of molecular etiologies.

METHODS

A population-based survey included adult patients with peripheral neuropathy from the province of Northern Ostrobothnia, Finland. Secondary causes of peripheral polyneuropathy were excluded and patients with clinical and neurophysiological features pertinent with CMT were included. Molecular diagnostics was carried out when DNA was available.

RESULTS

We found 107 subjects with CMT yielding a prevalence 34.6/100,000 in Northern Ostrobothnia. The heterozygous point mutation p.His123Arg in ganglioside induced differentiation associated protein 1 (GDAP1) was found in 31.5% and peripheral myelin protein 22 (PMP22) duplication in 16.9% of the affected. Point mutations in myelin protein zero, mitofusin 2, and gap junction protein beta 1 accounted for 6.7% of the cases. In addition, 18 persons had hereditary neuropathy with liability to pressure palsies and 15 of them carried the PMP22 deletion.

CONCLUSIONS

The prevalence of CMT in Northern Ostrobothnia, Finland, seems to be slightly higher than those in previous studies in European populations. Founder mutation in the GDAP1 gene accounts for a large part of the genetically defined CMT2 in Finland.

Epidemiologic Study of Charcot-Marie-Tooth Disease: A Systematic Review

BACKGROUND

Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy. CMT is classified into 2 main subgroups: CMT type 1 (CMT1; demyelinating form) and CMT type 2 (CMT2; axonal form). The objectives of this study were to systematically review and assess the quality of studies reporting the incidence and/or prevalence of CMT worldwide.

SUMMARY

A total of 802 studies were initially identified, with only 12 meeting the inclusion criteria. CMT prevalence was reported in 10 studies and ranged from 9.7/100,000 in Serbia to 82.3/100,000 in Norway. The frequency of the main subtypes varied from 37.6 to 84% for CMT1 and from 12 to 35.9% for CMT2; the country with the lowest prevalence of CMT1 was Norway, and the country with the highest prevalence of CMT1 was Iceland; on the other hand, CMT2 was least prevalent in the United Kingdom and most prevalent in Norway.

KEY MESSAGES

This review reveals the gaps that still exist in the epidemiological knowledge of CMT around the world. Published studies are of varying quality and utilise different methodologies, thus precluding a robust conclusion. Additional research focusing on epidemiological features of CMT in different nations and different ethnic groups is needed.

Cavovarus deformity in Charcot-Marie-Tooth disease: is there a hindfoot equinus deformity that needs treatment?

Background

Charcot-Marie-Tooth disease (CMT), one of the most common hereditary neurologic disorders, often results in debilitating cavovarus foot deformities. The deformities are still not fully understood, and the treatment recommendations are consequently heterogeneous, often including calf muscle or Achilles tendon lengthening.

Methods

We examined 40 patients (80 feet) with CMT and bilateral cavovarus deformities (19 men and 21 women, mean age 33.6 ± 14.6 years) and the feet of a healthy control population of 13 individuals (7 men and 6 women, mean age 43.9 ± 10.8 years). In all cases 3D instrumented gait analysis results with both conventional Plug-in-Gait analysis and the Heidelberg Foot Measurement Method (HFMM) were used to determine the sagittal plane kinematics, dorsi-plantar flexion (DPF), tibio-talar dorsiflexion (TTDF), and medial arch angle (MAA), and the results of patients and the control group were compared using the 2 methods. Decreased and increased dorsiflexion using TTDF was defined as 1 standard deviation below or above the mean of the control. Comparisons were done using descriptive statistics, the Pearson correlation coefficient and ANOVA.

Results

The TTDF was found to be decreased in 18 of the 80 feet examined (22.5 %), normal in 31 feet (38.75 %), and increased in 31 feet (38.75 %). The Pearson coefficient showed a positive correlation with R = 0.765, p < 0.001 between decreased TTDF values found by HFMM and decreased DPF values found with conventional Plug-in-Gait analysis, but a very weak correlation in patients with normal TTDF (R = -0.118) and increased TTDF (R = 0.078). Also, in patients with decreased TTDF values, there was a weak to moderate correlation with the MAA (R = 0.335), but no correlation between the MAA and DPF (R = 0.023).

Conclusions

The HFMM, unlike the conventional Plug-in-Gait analysis, distinguishes between the segments of the foot in foot deformities and facilitates evaluation of the hindfoot equinus component in patients with CMT and cavovarus deformity. Although there is a significant correlation between decreased TTDF with HFMM and decreased DPF with conventional Plug-in-Gait analysis, this correlation was not seen in patients with normal or increased TTDF values. Conventional Plug-in-Gait analysis alone does not indicate if an increased plantar flexion deformity is the result of either a cavus deformity or hindfoot equinus deformity, which limits its usefulness in assisting in treatment decision making.

Charcot-Marie-Tooth disease: frequency of genetic subtypes and guidelines for genetic testing

BACKGROUND

Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous group of diseases with approximately 45 different causative genes described. The aims of this study were to determine the frequency of different genes in a large cohort of patients with CMT and devise guidelines for genetic testing in practice.

METHODS

The genes known to cause CMT were sequenced in 1607 patients with CMT (425 patients attending an inherited neuropathy clinic and 1182 patients whose DNA was sent to the authors for genetic testing) to determine the proportion of different subtypes in a UK population.

RESULTS

A molecular diagnosis was achieved in 62.6% of patients with CMT attending the inherited neuropathy clinic; in 80.4% of patients with CMT1 (demyelinating CMT) and in 25.2% of those with CMT2 (axonal CMT). Mutations or rearrangements in PMP22, GJB1, MPZ and MFN2 accounted for over 90% of the molecular diagnoses while mutations in all other genes tested were rare.

CONCLUSION

Four commonly available genes account for over 90% of all CMT molecular diagnoses; a diagnostic algorithm is proposed based on these results for use in clinical practice. Any patient with CMT without a mutation in these four genes or with an unusual phenotype should be considered for referral for an expert opinion to maximise the chance of reaching a molecular diagnosis.

Pressure characteristics in painful pes cavus feet resulting from Charcot-Marie-Tooth disease

Charcot-Marie-Tooth (CMT) disease often presents with peripheral muscle imbalance associated with a painful cavus (medial high-arched) foot deformity which becomes increasingly severe and rigid as the disease progresses. The purpose of this study was to investigate the effect of pes cavus on foot pain and dynamic plantar pressure in CMT, and to explore the relationships between plantar pressure and pain. Sixteen participants diagnosed with CMT and painful pes cavus were assessed for foot posture, ankle dorsiflexion range of motion, levels of foot pain, functional impairment, health-related quality of life and plantar pressure distribution while walking. Plantar pressure parameters (mean pressure, peak pressure, pressure-time integral) and contact duration were measured using the Novel Pedar in-shoe capacitance transducer system and the foot was divided into rearfoot, midfoot and forefoot regions for analysis. Increasing cavus foot deformity was associated with more widespread foot pain and increased pressure under the forefoot and midfoot regions. In contrast, peak pressure decreased under the rearfoot. Neither relationship was found between foot pain intensity and any of the pressure variables, nor was ankle dorsiflexion range of motion correlated with pain location, intensity or degree of pes cavus. Although pes cavus in CMT is associated with substantial pain and dysfunction, there is no clear link between foot pain and plantar pressure. The more severe the degree of pes cavus, however, the more pressure develops under the lateral margin of the foot; probably as a result of the changed foot-ground contact seen during gait.

Gap junction protein beta 1 (GJB1) mutations and central nervous system symptoms in X-linked Charcot-Marie-Tooth disease

OBJECTIVES

To clarify the clinical variability, including central nervous system (CNS) involvement, in X-linked Charcot-Marie-Tooth disease (CMTX) patients.

MATERIAL AND METHODS

We clinically, pathologically and genetically studied six CMTX patients with distinct symptoms and four different GJB1 mutations.

RESULTS

One patient with Val63Ile had deafness, low intelligence, saccadic eye movement, upper extremity distal dominant muscle weakness and normal sensation. Another patient with Glu186Lys had severe sensorineural deafness at the age of 6 years, but did not develop muscle weakness until the age of 20 years. Two patients with Arg22Gln had typical CMT1A-like clinical features, no CNS symptoms and obvious onion bulb formations. Two siblings with deletion of the entire GJB1 gene had mild to moderate lower extremity muscle weakness and sensory disturbance without CNS involvement.

CONCLUSION

These findings suggest that some gain of function mutations of GJB1 may be related to CNS symptoms because the patients with GJB1 deletion only had peripheral neuropathy, although other unknown associated factors may contribute to their clinical phenotypes.

Immunological study of hereditary motor and sensory neuropathy type 1a (HMSN1a)

OBJECTIVES

Fifty three patients were studied to investigate whether autoimmune or inflammatory mechanisms could explain the phenotypic heterogeneity of patients with hereditary motor and sensory neuropathy type 1a (HMSN1a).

METHODS

Serum samples were examined for antibodies to peripheral nerve myelin protein 22 (PMP22), ganglioside GM1 and cauda equina homogenate, and interleukin-6 (IL-6) and soluble tumour necrosis factor receptor 1 (sTNF R1) concentrations. Serological results were compared with those from patients with other neuropathies (ONPs, n=30) and with normal subjects (n=51).

RESULTS

In the group as a whole, no relation emerged between clinical severity and any immune parameters. Immunohistochemical examination of four sural nerve biopsies did not show significant inflammatory infiltration. In a subset of 12 patients who experienced stepwise progression of disease, there was a trend towards a higher proportion having anti-PMP22 antibodies (33% v 15% of those with gradual disease progression, 3% ONPs, and no normal controls) and complement fixing antibodies to human cauda equina (25% v 5% with gradual progression, 8.6% ONPs, 3.9% normal controls, p=0.07).

CONCLUSIONS

Patients with HMSN1a and a stepwise disease progression may have an inflammatory, autoimmune component superimposed on the genetic condition.

Slowing of central conduction in X-linked Charcot-Marie-Tooth neuropathy shown by brain stem auditory evoked responses

BACKGROUND

The most common form of CMT with slow nerve conduction velocities (CMT type I) is CMT1A, caused by a submicroscopic duplication of a region of DNA on chromosome 17 including the PMP22 gene. This gene is expressed in peripheral nerve but not in the CNS. The second most common form is CMTX, caused by mutations in the connexin32 gene in the X chromosome. Connexin32 is expressed both in brain and in peripheral nerve. These molecular variants are difficult to distinguish clinically.

METHODS

Brain stem auditory evoked responses (BAERs) were measured in patients with CTMX and CMT1A.

RESULTS

BAERs showed central conduction slowing in male patients with CMTX which did not overlap the normal range. Patients with CMT1A had a delay in wave I latency but otherwise normal responses. These results are consistent with the pattern of expression of PMP22 in the peripheral portion of the eighth nerve (myelinated by Schwann cells) and of connexin32 in the central portion in the brainstem auditory pathways (myelinated by oligodendrocytes). This is the first evidence for central involvement in CMTX.

CONCLUSION

BAERs are useful to distinguish CMTX from CMT1A and may assist selection of appropriate patients for connexin32 mutation analysis.