Charcot-Marie-Tooth disease type 1A duplication with severe paresis of the proximal lower limb muscles: a long-term follow-up study

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.

Intraepineurial fat quantification and cross-sectional area analysis of the sciatic nerve using MRI in Charcot-Marie-Tooth disease type 1A patients

The objectives of this study were to assess the fat fraction (FF) and cross-sectional area (CSA) of the sciatic nerve in Charcot-Marie-Tooth disease type 1A (CMT1A) patients using Dixon-based proton density fat quantification MRI and to elucidate its potential association with clinical parameters. Thigh MRIs of 18 CMT1A patients and 18 age- and sex-matched volunteers enrolled for a previous study were reviewed. Analyses for FF and CSA of the sciatic nerve were performed at three levels (proximal to distal). CSA and FF were compared between the two groups and among the different levels within each group. The relationship between the MRI parameters and clinical data were assessed in the CMT1A patients. The CMT1A patients showed significantly higher FF at level 3 (p = 0.0217) and significantly larger CSA at all three levels compared with the control participants (p < 0.0001). Comparisons among levels showed significantly higher FF for levels 2 and 3 than for level 1 and significantly larger CSA for level 2 compared with level 1 in CMT1A patients. CSA at level 3 correlated positively with the CMT neuropathy score version 2 (CMTNSv2). In conclusion, the sciatic nerve FF of CMT1A patients was significantly higher on level 3 compared with both the controls and the measurements taken on more proximal levels, suggesting the possibility of increased intraepineurial fat within the sciatic nerves of CMT1A patients, with a possible distal tendency. Sciatic nerve CSA at level 3 correlated significantly and positively with CMTNSv2, suggesting its potential value as an imaging marker for clinical severity.

Muscular atrophy and weakness in the lower extremities in Behçet’s disease: A case report and review of literature

BACKGROUND

In Behçet’s disease (BD), very few cases of muscular involvement have been reported previously. The natural history and therapeutic protocol for muscular involvement in BD are obscure due to the low incidence of peripheral neuropathy or myopathy in BD. The purpose of our study was to report a rare case of BD with chronic, focal forms of neuromyopathy and review the relevant literature.

CASE SUMMARY

We herein report the case of a 54-year-old man who presented with progressive muscular atrophy and weakness of both thighs 2 years after the presentation of the cardinal symptoms of BD. The past medical history, electrophysiological study, neurological examination, blood tests, magnetic resonance imaging study, and histological exam were performed for the differential diagnosis. Relevant literature on muscular involvement in BD was reviewed. Neurological examination revealed that muscular involvement was predominantly localized in the proximal parts of the lower extremities. Heterogeneous enhancement of several thigh muscles was observed on magnetic resonance imaging, which corresponded with the clinical manifestations. Histological study of one of the enhanced muscles showed denervation atrophy of the muscle with superimposed myopathic changes, while electrophysiological studies only suggested denervation.

CONCLUSION

To our knowledge, this is the first case of neurogenic muscular atrophy with a specific set of clinical, radiological, electrophysiological, and histological findings reported in BD.

New evidence for secondary axonal degeneration in demyelinating neuropathies

Development of peripheral nervous system (PNS) myelin involves a coordinated series of events between growing axons and the Schwann cell (SC) progenitors that will eventually ensheath them. Myelin sheaths have evolved out of necessity to maintain rapid impulse propagation while accounting for body space constraints. However, myelinating SCs perform additional critical functions that are required to preserve axonal integrity including mitigating energy consumption by establishing the nodal architecture, regulating axon caliber by organizing axonal cytoskeleton networks, providing trophic and potentially metabolic support, possibly supplying genetic translation materials and protecting axons from toxic insults. The intermediate steps between the loss of these functions and the initiation of axon degeneration are unknown but the importance of these processes provides insightful clues. Prevalent demyelinating diseases of the PNS include the inherited neuropathies Charcot-Marie-Tooth Disease, Type 1 (CMT1) and Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) and the inflammatory diseases Acute Inflammatory Demyelinating Polyneuropathy (AIDP) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). Secondary axon degeneration is a common feature of demyelinating neuropathies and this process is often correlated with clinical deficits and long-lasting disability in patients. There is abundant electrophysiological and histological evidence for secondary axon degeneration in patients and rodent models of PNS demyelinating diseases. Fully understanding the involvement of secondary axon degeneration in these diseases is essential for expanding our knowledge of disease pathogenesis and prognosis, which will be essential for developing novel therapeutic strategies.

Texture analysis using T1-weighted images for muscles in Charcot-Marie-Tooth disease patients and volunteers

OBJECTIVES

To explore whether texture features using T1-weighted images correlate with fat fraction, and whether they differ between Charcot-Marie-Tooth (CMT) disease patients and volunteers.

METHODS

The institutional review board approved this retrospective study, and the requirement for informed consent was waived; data of eighteen CMT patients and eighteen healthy volunteers from a previous study was used. Texture features of the muscles including mean, standard deviation (SD), skewness, kurtosis, and entropy of the signal intensity were derived from T1-weighted images. Spearman's correlation analysis was used to assess the relationship between texture features and fat fraction measured by 3D multiple gradient echo Dixon-based sequence. Mann-Whitney U test was used to compare the texture features between CMT patients and volunteers. Intraobserver and interobserver agreements for the texture features were assessed using the intraclass correlation coefficient.

RESULTS

The SD (ρ = 0.256, p < 0.001) and entropy (ρ = 0.263, p < 0.001) were significantly and positively correlated with fat fraction; skewness (ρ = - 0.110, p = 0.027) and kurtosis (ρ = - 0.149, p = 0.003) were significantly and inversely correlated with fat fraction. The CMT patients showed a significantly higher SD (63.45 vs. 49.26; p < 0.001), skewness (1.06 vs. 0.56; p < 0.001), kurtosis (4.00 vs. 1.81; p < 0.001), and entropy (3.20 vs. 3.02; p < 0.001) than did the volunteers. Intraobserver and interobserver agreements were almost perfect for mean, SD, and entropy.

CONCLUSIONS

Texture features using T1-weighted images correlated with fat fraction and differed between CMT patients and volunteers.

KEY POINTS

• Standard deviation and entropy of muscles derived from T1-weighted images were significantly and positively correlated with the muscle fat fraction. • Mean, standard deviation, and entropy were considered highly reliable in muscle analyses. • Texture features may have the potential to diagnose early stage of intramuscular fatty infiltration.

Changes in walking velocity and stride parameters with age in children with Charcot-Marie-Tooth disease

The purpose of this study is to assess how Charcot-Marie-Tooth disease, a group of inherited peripheral neuropathies that result in distal weakness, affects walking velocity over time in comparison to age-matched controls. Comprehensive gait analysis of 57 children (mean age 12.0, SD 3.7 years) compared to 76 age-matched controls (mean age 10.1, SD 3.4 years) demonstrated slower walking velocity (p<0.001) due to both shorter stride length (p<0.001) and diminished cadence (p=0.01). There was higher walking velocity (p<0.001), stride length (p=0.002) and cadence (p<0.001) in patients with dorsiflexor strength ≥3 and higher walking velocity (p=0.001) and cadence (p=0.03) in patients plantar flexor strength ≥4. Analysis of Charcot-Marie-Tooth type 1 and type 2 subgroups showed that walking velocity increased significantly with age in controls (p=0.001) but did not increase in children with either subtype (p>0.54). Stride length increased significantly with age in all groups (p<0.001) but at a slower rate in type 1 and 2 compared to controls. These differences contributed to increasing deficits in walking velocity and stride length with age in type 1 and 2 in comparison to controls, with deficits appearing earlier in type 2. Since the slower walking velocity in children with Charcot-Marie-Tooth disease is primarily due to short stride length, treatments that enable improved stride length, such as plantar flexor strengthening and bracing, may improve walking velocity and associated gait function.

Muscle fat quantification using magnetic resonance imaging: case-control study of Charcot-Marie-Tooth disease patients and volunteers

BACKGROUND

This study aimed to evaluate the potential value of 3D multiple gradient echo Dixon-based magnetic resonance imaging (MRI) sequence as a tool for thigh intramuscular fat quantification in Charcot-Marie-Tooth disease (CMT) patients.

METHODS

A prospective comparison study comprising 18 CMT patients and 18 age/sex-matched volunteers was performed. MRI including 3D multiple gradient echo Dixon-based imaging was performed for each subject. Region of interest analyses were performed at the upper and lower third of both thighs. The two-sample t-test or Wilcoxon rank sum test was used for intergroup comparison of the mean muscle fat fraction. Intraclass correlation coefficients were used to evaluate the interobserver agreement and test-retest reproducibility. Semiquantitive analysis using the Goutallier classification (Grades 0-4) was performed on T1-weighted images in upper thigh muscles. For Goutallier Grade 0 muscles, comparison of the mean intramuscular fat fraction between volunteers and CMT patients was performed.

RESULTS

The interobserver agreements were excellent for all measurements (intraclass correlation coefficients > 0.8). Mean muscle fat fractions were significantly higher in all the measured muscles of CMT patients (P < 0.05) except in the adductor magnus in the upper thigh (P = 0.109). Goutallier Grade 0 muscles of the CMT patients showed a significantly higher mean fat fraction compared with that of the volunteers (P < 0.05).

CONCLUSIONS

3D multiple gradient echo Dixon-based MRI is a reproducible and sensitive technique which can reveal a significant difference in the fat fraction of thigh muscle, including comparison between Goutallier Grade 0 muscles, between CMT patients and volunteers.

NEFL E396K mutation is associated with a novel dominant intermediate Charcot-Marie-Tooth disease phenotype

The purpose of the study was to describe a pedigree with NEFL E396K mutation associated with a novel dominant intermediate Charcot-Marie-Tooth disease (DI-CMT) phenotype. The pedigree comprised four patients over two generations, aged between 35 and 59 years, who have been serially evaluated since 1993. Their clinical picture was characterized by pes cavus, sensorimotor neuropathy and spastic gait. Both older patients showed ascending leg weakness to involve pelvic musculature. CMT neuropathy score ranged from 14 to 26 (moderate to severe disease). Electrophysiology showed uniform nerve conduction slowing in the intermediate range, both in distal and proximal nerve segments. Multimodal evoked potential and blink reflex studies revealed abnormalities indicative of central sensorimotor pathway dysfunction. On imaging studies of lower-limb musculature, there was massive atrophy of intrinsic foot muscles and to a lesser degree of calves and thighs predominating in muscles innervated by tibial and sciatic nerves. In both patients exhibiting waddling gait, there was atrophy of pelvic muscles mainly involving gluteus medius, gluteus minimus and piriformis. We conclude that NEFL E396K mutation may manifest with a novel DI-CMT phenotype, characterized by simultaneous involvement of the peripheral and central nervous system.

Evolution of Charcot-Marie-Tooth disease type 1A duplication: a 2-year clinico-electrophysiological and lower-limb muscle MRI longitudinal study

The objective of this study was to analyze Charcot-Marie-Tooth disease type 1A (CMT1A) evolution. We conducted a 2-year longitudinal study in 14 CMT1A patients and 14 age- and sex-matched controls. In the patients, we performed neurological examination with hand-held dynamometry, electrophysiology, and lower-limb muscle MRI, both at baseline and 2 years later, while controls were examined at baseline only. Patients' ages ranged from 12 to 51 years. Outstanding manifestations on initial evaluation included pes cavus, areflexia, lower-limb weakness, and foot hypopallesthesia. In evaluating muscle power, good correlation was observed between manual testing and dynamometry. Compared to controls, Lunge, 10-Meter-Walking, and 9-Hole-Peg tests were impaired. Their CMT neuropathy score and functional disability scale showed that patients exhibited mild phenotype and at most slight walking difficulty. Electrophysiology revealed marked nerve conduction slowing and variable compound muscle action potential amplitude reduction. On lower-limb muscle MRI, there was distally accentuated fatty infiltration accompanied by edema in calf muscles. All these clinico-electrophysiological and imaging findings remained almost unaltered during monitoring. Using multivariate analysis, no significant predictors of progression associated to the disease were obtained. We conclude that in the 2-year period of study, CMT1A patients showed mild progression with good concordance between clinico-electrophysiological and imaging findings.

Ataxia of Charlevoix-Saguenay: MR and Clinical Results in Lower-Limb Musculature

OBJECTIVE

Peripheral neuropathy is a cardinal manifestation of the autosomal recessive spastic ataxia of Charlevoix- Saguenay (ARSACS), although its type of neuromuscular involvement has not been definitely established, and magnetic resonance imaging (MRI) plays an important role in the assessment of muscle and nerve diseases. The objective of this work has been to define the patterns of muscle weakness and of abnormal muscular MRI in ARSACS.

PATIENTS AND METHODS

Five patients with a molecular diagnosis of ARSACS, aged 39 to 59 years, whose electrophysiological findings were consistent with an axonal neuropathy of distal distribution superimposed on a developmental defect of myelinization, underwent neurological and MRI lower-limb examinations. Conventional FSE T1-weighted and STIR sequences were performed, looking for fatty infiltration and oedema in the musculature of the thighs, legs and feet, together with their distribution along the longitudinal axis of the muscle bellies.

RESULTS

On clinical examination, paralysis was apparent in foot muscles; moderate weakness, in leg musculature; and normal strength, in thigh muscles. MRI demonstrated massive fat deposition in the foot muscles and medial gastrocnemii in every case, distal fat infiltration and oedema in every leg muscle group, and preservation of thigh muscles, albeit with diffuse minimal non-specific fat infiltration. An inverse correlation between strength and degree of fat infiltration in lower-limb muscles became apparent.

CONCLUSION

The preponderance of weakness and MRI abnormalities in distal muscle groups was concordant with the presence of a length-dependent axonopathy, as described in ARSACS.

Ataxie de Charlevoix-Saguenay : IRM et observations cliniques au niveau de la musculature des membres inférieurs.

A novel Lys141Thr mutation in small heat shock protein 22 (HSPB8) gene in Charcot-Marie-Tooth disease type 2L

Charcot-Marie-Tooth disease (CMT) is a group of clinically and genetically heterogeneous peripheral neuropathies. HSPB8 gene encodes heat shock protein 22 (HSP22) which belongs to the superfamily of small stress induced proteins. Mutations in HSPB8 are implicated to CMT2L and distal hereditary motor neuropathy 2A (dHMN2A). All three reported HSPB8 mutations are interestingly located in the Lys141 residue. In the present study, we examined a Korean axonal CMT patient who presented distal limb atrophy, sensory loss, areflexia, and axonal loss of large myelinated fibers. Whole exome sequencing identified a novel missense mutation c.422A>C (p.Lys141Thr) in HSPB8 as the underlying cause of the CMT2 patient. The mutation was regarded as a de novo case because both unaffected parents have no such mutation. The patient with HSPB8 mutation is the first case in Koreans. Clinical heterogeneities have been revealed in patients with Lys141 mutation; the present patient revealed similar phenotype of CMT2L. In addition, the lower limb MRI revealed a similarity between our HSPB8 and HSPB1 patients. It seems that the Lys141 site in the alpha-crystallin domain of HSPB8 is regarded as a mutational hot spot for peripheral neuropathy development, and mutations even in the same codon can exhibit different CMT phenotypes.

[Autopsy case of a patient with Charcot-Marie-Tooth disease type 1A and suspected chronic inflammatory demyelinating polyradiculoneuropathy, which was later diagnosed as amyotrophic lateral sclerosis]

We report an autopsy case of a 74-year-old man with late onset Charcot-Marie-Tooth disease type 1A (CMT1A) diagnosed by genetic screening, later associated with amyotrophic lateral sclerosis (ALS). At the age of 70 years, the patient was admitted to our hospital because of progressive weakness and dysesthesia in the right upper limb. In the early stages of the illness, he was diagnosed with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and transient improvement was achieved with intravenous immunoglobulin. However, the symptoms progressively worsened and became refractory. Gene analysis revealed PMP22 gene duplication, which confirmed CMT1A. On sural nerve biopsy, severe demyelinating neuropathy and abundant onion-bulb formations with endoneurial infiltration of inflammatory cells were observed. Thereafter, pseudo-bulbar palsy and respiratory muscle weakness developed insidiously and progressed rapidly along with muscle weakness in the limbs and trunk. The patient died about four years after the onset of this disease. Postmortem examination showed moderate neuronal cell loss, Bunina bodies, and TDP-43-positive inclusions in the anterior horn cells. The spinal cord revealed axonal loss and extensive macrophage permeation in the corticospinal tracts. On the basis of these findings, the final neuropathological diagnosis was ALS. This is the first report of an autopsy case of CMT1A complicated with ALS. We here discuss the significant clinical and neuropathological findings of this case.

MRI findings, patterns of disease distribution, and muscle fat fraction calculation in five patients with Charcot-Marie-Tooth type 2 F disease

PURPOSE

To describe the magnetic resonance imaging (MRI) pattern of muscle involvement and disease progression in five patients with late-onset Charcot-Marie-Tooth (CMT) disease type 2 F, due to a previously unknown mutation.

MATERIALS AND METHODS

Five patients (three males, two females) underwent MRI of the lower limbs to define the pattern of muscle involvement and evaluate the muscle fat fraction (MFF) of residual thigh muscle with gradient-echo (GRE) dual-echo dual-flip angle technique. Evaluation of fatty infiltration both by visual inspection and MFF calculation was performed.

RESULTS

A proximal-to-distal gradient of muscle involvement was depicted in male patients with extensive muscle wasting of lower legs, less severe impairment of distal thigh muscles, and sparing of proximal thigh muscles. A peculiar phenotype finding was that no or only slight muscle abnormalities could be found in the two female patients.

CONCLUSION

We described the pattern of muscle involvement and disease progression in a family with CMT disease type 2 F. GRE dual-echo dual-flip angle MRI technique is a valuable technique to obtain a rapid quantification of MFF.

Pes cavus and hereditary neuropathies: when a relationship should be suspected

The hereditary peripheral neuropathies are a clinically and genetically heterogeneous group of diseases of the peripheral nervous system. Foot deformities, including the common pes cavus, but also hammer toes and twisting of the ankle, are frequently present in patients with hereditary peripheral neuropathy, and often represent one of the first signs of the disease. Pes cavus in hereditary peripheral neuropathies is caused by imbalance between the intrinsic muscles of the foot and the muscles of the leg. Accurate clinical evaluation in patients with pes cavus is necessary to exclude or confirm the presence of peripheral neuropathy. Hereditary peripheral neuropathies should be suspected in those cases with bilateral foot deformities, in the presence of family history for pes cavus and/or gait impairment, and in the presence of neurological symptoms or signs, such as distal muscle hypotrophy of limbs. Herein, we review the hereditary peripheral neuropathies in which pes cavus plays a key role as a "spy sign," discussing the clinical and molecular features of these disorders to highlight the importance of pes cavus as a helpful clinical sign in these rare diseases.

[Wide spectrum of hereditary motor sensory neuropathy (HMSN)]

Hereditary neuropathies are classified into HMSN/Charcot-Marie-Tooth disease (CMT), familial amyloid polyneuropathy (FAP), hereditary motor neuropathies (HMN) and hereditary sensory (and autonomic) neuropathies (HSAN). The clinical features of HMSN are generally characterized as distal dominant motor and sensory involvements. However, we have reported a novel HMSN with proximal dominancy (HMSN-P) originated in Okinawa and Shiga prefectures, Japan. The gene locus is located in the centromere region of chromosome 3. In 2008, a new family with the HMSN-P was reported from Brazilians of Japanese ancestry. This Brazilian family was initially diagnosed as having "a familial ALS". The HMSN-P linked to ch.3 is not limited in Japan, but may be present in the worldwide. The overseas scientific research for the elucidation of the mechanism of HMSN-P supported by JSPS KAKENHI (21406026) is planning. Recently several other types of HMSN-P have been reported; HMSN-P with urinary disturbance and paroxysmal dry cough, a patient with both CMT 1A and mild spinal muscular atrophy and CMT1A with severe paresis of the proximal lower limb muscles. Therefore the clinical concept of HMSN is not limited as the disease with distal dominant motor sensory involvement. HMSN has the wider spectrum from distal to proximal and motor/sensory to autonomic neuropathies.

Clinical progression in Charcot-Marie-Tooth disease type 1A duplication: clinico-electrophysiological and MRI longitudinal study of a family

Long-term follow-up studies in Charcot-Marie-Tooth disease type 1 duplication (CMT1A) are scanty. Here we describe a longitudinal study in a CMT1A pedigree. Our CMT1A pedigree comprised 11 examined patients, ages between 13 and 83 (median, 36) years, serially evaluated for up to 26 years. In all 11 patients we carried out electrophysiological evaluation, and in three of them magnetic resonance imaging (MRI) of lower-limb musculature. The 54-year-old proband patient, yearly examined as of age 28, developed at age 48 gradual and progressive distal lower-leg weakness ascending to thigh musculature. His serial electrophysiological studies showed diffuse slowing of motor conduction velocity, absence or severe attenuation of distal compound muscle action potentials, and spontaneous muscle activity in the tibialis anterior and rectus femoris. Two MRI studies of lower limbs, at ages 51 and 54, showed extensive fatty atrophy of lower-leg musculature, and progressive and distally accentuated fatty atrophy of anterior and posterior femoral muscles. An outstanding finding in the first MRI was the presence of marked edema of anterior femoral musculature, which to a great degree was replaced by fatty atrophy in the second study. Muscle edema was also noted in lower-leg and posterior femoral musculature. There was minimal fatty atrophy of the gluteus maximus, the remaining pelvic muscles being preserved. The other ten patients showed mild or moderate phenotype, which remained quiescent over the period of observation. Electrophysiological studies disclosed diffuse and uniform slowing of nerve conduction velocities; in no case was spontaneous muscle activity recorded. MRI showed the CMT1A characteristic pattern of distally accentuated fatty atrophy involving foot and lower-leg musculature with preservation of thigh musculature. We conclude that a small proportion of patients with CMT1A develop a late progression of disease manifested with accentuated distal leg weakness ascending to involve thigh musculature, and that long-term follow-up is essential for its detection.

Phenotype and clinical evolution of Charcot-Marie-Tooth disease type 1A duplication

In this paper we revise the phenotype and clinical evolution of Charcot-Marie-Tooth disease type 1A duplication (CMT1A). We mainly focus on four phenotypic hallmarks: (i) "classic" phenotype, as currently observed in proband patients; (ii) evolution of mild phenotype of secondary cases in infancy and early childhood; (iii) proximal lower-limb musculature involvement as a late phenotypic feature; and (iv) minimal adult phenotype. We also briefly revise genetic, electrophysiological, pathological and neuroimaging data of the disease.

Distal hereditary motor neuropathy in Korean patients with a small heat shock protein 27 mutation

Distal hereditary motor neuropathy (dHMN) is a heterogeneous disorder characterized by degeneration of motor nerves in the absence of sensory abnormalities. Recently, mutations in the small heat shock protein 27 (HSP27) gene were found to cause dHMN type II or Charcot-Marie-Tooth disease type 2F (CMT2F). The authors studied 151 Korean axonal CMT or dHMN families, and found a large Korean dHMN type II family with the Ser135Phe mutation in HSP27. This mutation was inherited in an autosomal dominant manner, and was well associated with familial members with the dHMN phenotype. This mutation site is located in the alpha-crystallin domain and is highly conserved between different species. The frequency of this HSP27 mutation in Koreans was 0.6%. Magnetic resonance imaging analysis revealed that fatty infiltrations tended to progressively extend distal to proximal muscles in lower extremities. In addition, fatty infiltrations in thigh muscles progressed to affect posterior and anterior compartments but to lesser extents in medial compartment, which differs from CMT1A patients presenting with severe involvements of posterior and medial compartments but less involvement of anterior compartment. The authors describe the clinical and neuroimaging findings of the first Korean dHMN patients with the HSP27 Ser135Phe mutation. To our knowledge, this is the first report of the neuroimaging findings of dHMN type II.

Distal hereditary motor neuropathy in Korean patients with a small heat shock protein 27 mutation

Distal hereditary motor neuropathy (dHMN) is a heterogeneous disorder characterized by degeneration of motor nerves in the absence of sensory abnormalities. Recently, mutations in the small heat shock protein 27 (HSP27) gene were found to cause dHMN type II or Charcot-Marie-Tooth disease type 2F (CMT2F). The authors studied 151 Korean axonal CMT or dHMN families, and found a large Korean dHMN type II family with the Ser135Phe mutation in HSP27. This mutation was inherited in an autosomal dominant manner, and was well associated with familial members with the dHMN phenotype. This mutation site is located in the alpha-crystallin domain and is highly conserved between different species. The frequency of this HSP27 mutation in Koreans was 0.6%. Magnetic resonance imaging analysis revealed that fatty infiltrations tended to progressively extend distal to proximal muscles in lower extremities. In addition, fatty infiltrations in thigh muscles progressed to affect posterior and anterior compartments but to lesser extents in medial compartment, which differs from CMT1A patients presenting with severe involvements of posterior and medial compartments but less involvement of anterior compartment. The authors describe the clinical and neuroimaging findings of the first Korean dHMN patients with the HSP27 Ser135Phe mutation. To our knowledge, this is the first report of the neuroimaging findings of dHMN type II.