Diabetes mellitus exacerbates motor and sensory impairment in CMT1A

Abstract Charcot‐Marie‐Tooth disease type 1A (CMT1A) is caused by a duplication of PMP22 on chromosome 17 and is the most commonly inherited demyelinating neuropathy. Diabetes frequently causes predominantly sensory neuropathy. Whether diabetes exacerbates CMT1A is unknown. We identified 10 patients with CMT1A and diabetes and compared their impairment with 48 age‐matched control patients with CMT1A alone. Comparisons were made with the Charcot‐Marie‐Tooth disease (CMT) neuropathy score (CMTNS) and by electrophysiology. The CMTNS was significantly higher in patients with diabetes (20.25 ± 2.35) compared with controls (15.19 ± 0.69; p = 0.01). Values were particularly higher for motor signs and symptoms. Seven of the 10 diabetic patients had CMTNS >20 (severe CMT), while only 7 of the 48 age‐matched controls had scores >20. There was a trend for CMT1A patients with diabetes to have low compound muscle action potentials and sensory nerve action potentials, although nerve conduction velocities were not slower in diabetic patients compared with controls. Diabetes was associated with more severe motor and sensory impairment in patients with CMT1A.     

Early onset Charcot‐Marie‐Tooth neuropathy type 2A and severe developmental delay: expanding the clinical phenotype of MFN2‐related neuropathy

Charcot‐Marie‐Tooth (CMT) syndromes are a group of clinically heterogeneous disorders of the peripheral nervous system. Mutations of mitofusin 2 (MFN2) have been recognized to be associated with CMT type 2A (CMT2A). CMT2A is primarily an axonal disorder resulting in motor and sensory neuropathy. We report a male child with psychomotor delay, dysmorphic features, and weakness of lower limbs associated with electrophysiological features of severe, sensory‐motor, axonal neuropathy. The patient was diagnosed with early onset CMT2A and severe psychomotor retardation associated with c.310C>T mutation (p.R104W) in MFN2 gene. CMT2A should be considered in patients with both axonal sensory‐motor neuropathy and developmental delay.     

Novel GARS mutation presenting as autosomal dominant intermediate Charcot‐Marie‐Tooth disease

We report the first family with a glycyl‐tRNA synthetase (GARS) mutation with autosomal dominant intermediate Charcot‐Marie‐Tooth disease (DI‐CMT). The proband and the proband's father presented with gait disturbance and hand weakness. Both patients displayed moderately decreased conduction velocities (MNCV) (ranging from 29.2 to 37.8 m/s). A sural nerve biopsy of the father revealed evidence of both axonal loss and demyelination. On exome sequencing, in both the proband and his father, we identified a novel missense mutation (c.643G > C, p.Asp215His) in the GARS gene in a heterozygous state, which is considered to be pathogenic for this DI‐CMT family. The present study broadens current knowledge about intermediate CMT and the phenotypic spectrum of defects associated with GARS.     

Whole‐exome sequencing reveals a novel missense mutation in the MARS gene related to a rare Charcot‐Marie‐Tooth neuropathy type 2U

Charcot‐Marie‐Tooth (CMT) is a heterogeneous group of progressive disorders, characterized by chronic motor and sensory polyneuropathy. This hereditary disorder is related to numerous genes and varying inheritance patterns. Thus, many patients do not reach a final genetic diagnosis. We describe a 13‐year‐old girl presenting with progressive bilateral leg weakness and gait instability. Extensive laboratory studies and spinal magnetic resonance imaging scan were normal. Nerve conduction studies revealed severe lower limb peripheral neuropathy with prominent demyelinative component. Following presumptive diagnosis of chronic inflammatory demyelinating polyneuropathy, the patient received treatment with steroids and intravenous immunoglobulins courses for several months, with no apparent improvement. Whole‐exome sequencing revealed a novel heterozygous c.2209C>T (p.Arg737Trp) mutation in the MARS gene (OMIM 156560). This gene has recently been related to CMT type 2U. In‐silico prediction programs classified this mutation as a probable cause for protein malfunction. Allele frequency data reported this variant in 0.003% of representative Caucasian population. Family segregation analysis study revealed that the patient had inherited the variant from her 60‐years old mother, reported as healthy. Neurologic examination of the mother demonstrated decreased tendon reflexes, while nerve conduction studies were consistent with demyelinative and axonal sensory‐motor polyneuropathy. Our report highlights the importance of next‐generation sequencing approach to facilitate the proper molecular diagnosis of highly heterogeneous neurologic disorders. Amongst other numerous benefits, this approach might prevent unnecessary diagnostic testing and potentially harmful medical treatment.     

Late‐onset hereditary sensory and autonomic neuropathy expands the phenotypic spectrum of MFN2‐related diseases

Mutations in the Mitofusin 2 (MFN2) gene have been identified in patients with autosomal dominant axonal motor and sensory neuropathy or Charcot–Marie‐Tooth 2A (CMT2A). Here we describe clinical and pathological changes in an adult patient with sporadic hereditary sensory and autonomic neuropathy (HSAN) due to an MFN2 mutation. The patient was a 53‐year‐old man who had sensory involvement and anhidrosis in all limbs without motor features. The electrophysiological assessment documented severe axonal sensory neuropathy. The sural nerve biopsy confirmed the electrophysiological findings, revealing severe loss of myelinated and unmyelinated fibers with regeneration clusters. Genetic analysis revealed the previously identified mutation c.776 G > A in MFN2. Our report expands the phenotypic spectrum of MFN2‐related diseases. Sequencing of MFN2 should be considered in all patients presenting with late‐onset HSAN.     

腓骨肌萎缩症2A2A型家系的神经电生理及基因突变分析

目的探讨一个腓骨肌萎缩症(charcot-marie-tooth,CMT)家系的临床表现、神经电生理学和基因突变特点。方法收集家系先证者及其他成员的临床资料,对先证者进行神经电生理学检查和全外显子组基因测序,用Sanger测序技术对先证者及其家系进行突变位点验证。应用计算机软件预测突变位点氨基酸进化保守性和突变可能导致的蛋白质结构和功能变化,分析突变位点的性质。结果先证者儿童期发病,出现双下肢对称性肌肉无力伴跟腱反射消失及足部畸形,其母亲有类似症状。先证者神经电生理检查示运动和感觉神经纤维脱髓鞘及轴索性改变。基因检测发现先证者和母亲MFN2基因第11个外显子均检出c.1066A>G(p.T356A)杂合错义突变;先证者姐姐和父亲未检测到该突变。用PolyPhen-2和MutationTaster软件预测该突变为致病性,突变区域序列在不同物种间高度保守。结论儿童CMT2A2A患者的神经电生理、临床特点、发病机制及相关基因表型均有改变,此可为儿童CMT的临床诊断提供依据。     

A novel mutation of LRSAM1 in a Chinese family with Charcot‐Marie‐Tooth disease

Charcot‐Marie‐Tooth (CMT) disease is the most common inherited peripheral neuropathy characterized by progressive distal muscle weakness and atrophy with decreased or absent tendon reflexes. Mutations in LRSAM1 have been identified to cause CMT disease type 2P. We report a novel LRSAM1 mutation c.2021‐2024del (p.E674VfsX11) in a Chinese autosomal dominant CMT disease type 2 family. The phenotype was characterized by late onset and mild sensory impairment. Electrophysiological findings showed normal or mildly to moderately reduced motor and sensory nerve conduction velocities in lower and upper limb nerves.     

Spinal charcot‐marie‐tooth disease: A reappraisal

Introduction: Distal hereditary motor neuropathy (dHMN) is characterized by isolated distal muscle atrophy without sensory deficit. Nevertheless, clinical sensory loss has been reported despite preserved sensory nerve conduction in a few patients, thus differentiating these cases from the classical type 2 Charcot‐Marie‐Tooth disease (CMT2). Methods: We report 4 patients who presented with clinical sensory and motor neuropathy and normal peripheral sensory nerve conduction studies and were investigated with complete electrophysiological studies, including somatosensory evoked potentials (SEP). Results: These patients had a clinical presentation of classical CMT with isolated axonal motor neuropathy suggestive of dHMN. Interestingly, tibial nerve SEPs showed abnormalities suggestive of proximal involvement of dorsal roots that may explain the clinical somatosensory disturbances. Conclusions: These cases support the concept of spinal CMT that should be recognized as an intermediate form between dHMN and CMT2. SEP recording was helpful in defining a more precise phenotype of spinal CMT. Muscle Nerve 46: 603–607, 2012     

Rigid spine syndrome associated with sensory‐motor axonal neuropathy resembling Charcot–Marie‐Tooth disease is characteristic of Bcl‐2‐associated athanogene‐3 gene mutations even without cardiac involvement

Introduction: Bcl‐2‐associated athanogene‐3 (BAG3) mutations have been described in rare cases of rapidly progressive myofibrillar myopathies. Symptoms begin in the first decade with axial involvement and contractures and are associated with cardiac and respiratory impairment in the second decade. Axonal neuropathy has been documented but usually not as a key clinical feature. Methods: We report a 24‐year‐old woman with severe rigid spine syndrome and sensory‐motor neuropathy resembling Charcot–Marie–Tooth disease (CMT). Results: Muscle MRI showed severe fat infiltration without any specific pattern. Deltoid muscle biopsy showed neurogenic changes and discrete myofibrillar abnormalities. Electrocardiogram and transthoracic echocardiography results were normal. Genetic analysis of a panel of 45 CMT genes showed no mutation. BAG3 gene screening identified the previously reported c.626C>T, pPro209Leu, mutation. Discussion: This case indicates that rigid spine syndrome and sensory‐motor axonal neuropathy are key clinical features of BAG3 mutations that should be considered even without cardiac involvement. Muscle Nerve, 57 : 330–334, 2018     

Phenotype variability and histopathological findings in patients with a novel DNM2 mutation

Mutations of Dynamin 2 (DNM2) are responsible for several forms of neuromuscular disorder such as centronuclear myopathy, Charcot–Marie–Tooth disease (CMT) dominant intermediate type B, CMT 2M, and lethal congenital contracture syndrome 5. We describe a young man manifesting as length‐dependent sensorimotor neuropathy with hypertrophic cardiomyopathy, but his mother only had very mild symptoms of peripheral neuropathy. The electrophysiological data meet the criteria of intermediate CMT. The main pathological findings of sural nerve biopsy reveal a severe loss of large myelinating fibers and some clusters of regenerative fibers in fascicles, which are consistent with an axonal neuropathy. However, myopathological changes show a chronic myopathy‐like pattern characterized by great variations of fiber size, increased connective tissue, rimmed vacuoles and predominance of type 2 fibers. A novel DNM2 mutation (p.G359D) in the middle domain is identified, which is highly evolutionarily conserved. DNM2‐related CMT disease is phenotypically heterogeneous in age at onset, clinical features and electrophysiological changes. The histopathological findings indicate the coexistence of typical axonal neuropathy and chronic myopathy in DNM2‐related neuromuscular diseases.     

POLG mutations presenting as Charcot‐Marie‐Tooth disease

We report on two patients, with different POLG mutations, in whom axonal neuropathy dominated the clinical picture. One patient presented with late onset sensory axonal neuropathy caused by a homozygous c.2243G>C (p.Trp748Ser) mutation that resulted from uniparental disomy of the long arm of chromosome 15. The other patient had a complex phenotype that included early onset axonal Charcot‐Marie‐Tooth disease (CMT) caused by compound heterozygous c.926G>A (p.Arg309His) and c.2209G>C (p.Gly737Arg) mutations.     

Mutational mechanisms in MFN2‐related neuropathy: compound heterozygosity for recessive and semidominant mutations

Mitofusin‐2 (MFN2) mutations are the most common cause of autosomal dominant axonal Charcot‐Marie‐Tooth disease (CMT, type 2A), sometimes complicated by additional features such as optic atrophy (CMT6) and upper motor neuron involvement (CMT5). Several pathogenic mutations are reported, mainly acting in a dominant fashion, although few sequence variants behaved as recessive or semidominant in rare homozygous or compound heterozygous patients. We describe a 49‐year‐old woman with CMT5 associated with compound heterozygosity for two MFN2 variants, one already reported missense mutation (c.748C>T, p.R250W) and a novel nonsense sequence change (c.1426C>T, p.R476*). Her mother, carrying the p.R250W variant, had very late‐onset minimal axonal neuropathy, whilst the father harboring the nonsense sequence change had neither clinical nor electrophysiological neuropathy. The missense mutation is likely pathogenic according to in silico analyses and a previous report, while the nonsense variant is predicted to behave as a null allele. The p.R250W variant behaves as semidominant by causing only a mild, almost subclinical, neuropathy when heterozygous; the nonsense mutation in the father was phenotypically silent, suggesting that haploinsufficiency for MFN2 is not disease causative, but was deleterious in the daughter who had only one active mutated MFN2 allele.     

A novel mutation of gap junction protein β 1 gene in X-linked Charcot-Marie-Tooth disease

Introduction: In this study we report a novel mutation in the gap junction protein beta 1 (GJB1) gene of a Chinese X‐linked Charcot–Marie–Tooth disease (CMTX1) family, which has specific electrophysiological characteristics. Methods: Twenty members in the family were studied by clinical neurological examination and GJB1 gene mutation analysis, and 3 patients were studied electrophysiologically. The proband and his mother also underwent sural nerve biopsy. Results: All patients have the CMT phenotype, except for 2 asymptomatic carriers. Electrophysiological examinations showed non‐uniform slowing of motor conduction velocities and partial motor conduction blocks and temporal dispersion. Sural nerve biopsy confirmed a predominantly demyelinating neuropathy, and an Asn2Lys mutation in the amino‐terminal domain was found in 9 members of this family, but not in 25 normal controls in the family. Conclusions: This family represents a novel mutation in the GJB1 form of CMTX1. The mutation in the amino‐terminus has an impact on the electrophysiological characteristics of the disease. Muscle Nerve, 2011     

A novel INF2 mutation in a Korean family with autosomal dominant intermediate Charcot‐Marie‐Tooth disease and focal segmental glomerulosclerosis

Mutations in the inverted formin‐2 (INF2) gene were recently identified in patients with autosomal dominant intermediate Charcot‐Marie‐Tooth (DI‐CMT) disease and focal segmental glomerulosclerosis (FSGS). Here, we identified a novel p.L132P INF2 mutation in a Korean family with DI‐CMT and FSGS by whole‐exome sequencing. This mutation was cosegregated with affected individuals in the family and was not found in the 300 controls. The two affected members exhibited juvenile onset sensorimotor polyneuropathy and FSGS. Nerve conduction studies showed an intermediate range of motor nerve conduction velocities. We report a novel INF2 mutation in a family with DI‐CMT and FSGS as the first case in Koreans. The INF2 mutation appears to be a major cause of CMT with FSGS.     

Whole exome sequencing identifies three recessive FIG4 mutations in an apparently dominant pedigree with Charcot–Marie–Tooth disease

Charcot–Marie–Tooth disease (CMT) is genetically heterogeneous and classification based on motor nerve conduction velocity and inheritance is used to direct genetic testing. With the less common genetic forms of CMT, identifying the causative genetic mutation by Sanger sequencing of individual genes can be time-consuming and costly. Next-generation sequencing technologies show promise for clinical testing in diseases where a similar phenotype is caused by different genes. We report the unusual occurrence of CMT4J, caused by mutations in FIG4, in a apparently dominant pedigree. The affected proband and her mother exhibit different disease severities associated with different combinations of compound heterozygous FIG4 mutations, identified by whole exome sequencing. The proband was also shown to carry a de novo nonsense mutation in the dystrophin gene, which may contribute to her more severe phenotype. This study is a cautionary reminder that in families with two generations affected, explanations other than dominant inheritance are possible, such as recessive inheritance due to three mutations segregating in the family. It also emphasises the advantages of next-generation sequencing approaches that screen multiple CMT genes at once for patients in whom the common genes have been excluded.     

SEIPIN S90L Mutation in an Italian family with CMT2/dHMN and pyramidal signs

Heterozygous mutations in the Berardinelli–Seip congenital lipodystrophy (BSCL2) gene have been associated with different clinical phenotypes including Silver syndrome/spastic paraplegia 17, distal hereditary motor neuropathy type V, and Charcot–Marie–Tooth disease type 2 (CMT2) with predominant hand involvement. We studied an Italian family with a CMT2 phenotype with pyramidal signs that had subclinical sensory involvement on sural nerve biopsy. Direct sequencing analysis of the BSCL2 gene in the three affected siblings revealed an S90L mutation. This report confirms the variability of clinical phenotypes associated with a BSCL2 Ser90Leu mutation and describes the first Italian family with this mutation. Muscle Nerve, 2010     

Small heat shock protein B3 (HSPB3) mutation in an axonal Charcot‐Marie‐Tooth disease family

Heat shock protein B3 (HSPB3) gene encodes a small heat‐shock protein 27‐like protein which has a high sequence homology with HSPB1. A mutation in the HSPB3 was reported as the putative underlying cause of distal hereditary motor neuropathy 2C (dHMN2C) in 2010. We identified a heterozygous mutation (c.352T>C, p.Tyr118His) in the HSPB3 from a Charcot‐Marie‐Tooth disease type 2 (CMT2) family by the method of targeted next generation sequencing. The mutation was located in the well conserved alpha‐crystalline domain, and several in silico predictions indicated a pathogenic effect of the mutation. Clinical and electrophysiological features of the patients indicated the axonal type of CMT. Clinical symptoms without sensory involvements were similar between the present family and the previous family. Mutations in the HSPB1 and HSPB8 genes have been reported to be relevant with both types of CMT2 and dHMN. Our findings will help in the molecular diagnosis of CMT2 by expanding the phenotypic range due to the HSPB3 mutations.     

A novel NDRG1 mutation in a non‐Romani patient with CMT4D/HMSN‐Lom

Charcot‐Marie‐Tooth disease type 4D (CMT4D), also known as hereditary motor and sensory neuropathy Lom type (HMSNL), is an autosomal recessive, early onset, severe demyelinating neuropathy with hearing loss, caused by N‐Myc downstream‐regulated gene 1 (NDRG1) mutations. CMT4D is rare with only three known mutations, one of which (p.Arg148Ter) is found in patients of Romani ancestry and accounts for the vast majority of cases. We report a 38‐year‐old Italian female with motor development delay, progressive neuropathy, and sensorineural deafness. Magnetic resonance imaging showed slight atrophy of cerebellum, medulla oblongata, and upper cervical spinal cord. She had a novel homozygous NDRG1 frameshift mutation (c.739delC; p.His247ThrfsTer74). The identification of this NDRG1 mutation confirms that CMT4D is not a private Romani disease and should be considered in the differential diagnosis of recessive demyelinating CMT.     

Neurofilament light mutation causes hereditary motor and sensory neuropathy with pyramidal signs

To identify novel mutations causing hereditary motor and sensory neuropathy (HMSN) with pyramidal signs, a variant of Charcot‐Marie‐Tooth disease (CMT), we screened 28 CMT and related genes in four members of an affected Japanese family. Clinical features included weakness of distal lower limb muscles, foot deformity, and mild sensory loss, then late onset of progressive spasticity. Electrophysiological studies revealed widespread neuropathy. Electron microscopic analysis showed abnormal mitochondria and mitochondrial accumulation in the neurons and Schwann cells. Brain magnetic resonance imaging (MRI) revealed an abnormally thin corpus callosum. In all four, microarrays detected a novel heterozygous missense mutation c.1166A>G (p.Y389C) in the gene encoding the light‐chain neurofilament protein (NEFL), indicating that NEFL mutations can result in a HMSN with pyramidal signs phenotype.