Hereditary Sensory Neuropathy Research Articles

A Young Man With Hereditary Motor And Sensory Neuropathy: A Rare Genetic Association

Hereditary motor and sensory neuropathies with early onset are uncommon conditions that include Dejerine-Sottas neuropathy, which begins in infancy, and congenital hypomyelinating neuropathy, which manifests in the early postnatal period. However, these two historically defined disease entities are only small parts of the clinical spectrum. It is well recognized that very early onset hereditary neuropathies are frequently caused by de novo dominant mutations in PMP22, MPZ, and EGR2. In addition, mutations in several other dominant and recessive genes for Charcot-Marie-Tooth disease may lead to similar phenotypes. A 20-year-old boy had complaints of weakness of both lower limbs for 1 year, followed by wasting and foot drop, which subsequently involved the upper limbs. Nerve conduction velocity and electromyography of both lower limbs revealed demyelinating sensory motor polyneuropathy. Histological examination of the sural nerve revealed a nerve trunk with perineural soft tissue, with the nerve bundles being irregular and separated by fibrous tissue bands. The later reveals small perivascular infiltration of chronic inflammatory cells, and no granuloma or AFB is seen. The genetic test of whole exome screening for heriditatory neuropathy showed pathogenic (PM2, PVS, PP5) with a gene impact of (NF2: c.363+1G>T), which is a rare entity in our case study to consider the diagnosis despite negative family history. We highlight this rare disease in young man with a high index of clinical suspicion for its diagnosis. Bangladesh J Medicine 2024; 35: 101-105

A novel NTRK1 splice site variant causing congenital insensitivity to pain with anhidrosis in a Chinese family

BackgroundCongenital insensitivity to pain with anhidrosis (CIPA, OMIM #256800), also known as hereditary sensory and autonomic neuropathy type Ⅳ (HSAN-IV), is a rare autosomal recessive disorder characterized by recurrent episodic fevers, anhidrosis, insensitivity to noxious stimuli, self-mutilating behavior and intellectual disability. CIPA can be caused by the variants in NTRK1 gene, which encodes a high-affinity tyrosine kinase receptor for nerve growth factor. To ascertain the hereditary cause of a patient with CIPA accompanied by the additional symptoms of mild growth retardation, prone to fracture, underdeveloped nails of fingers and toes, irregular tooth alignment, enamel hypoplasia, postoperative wound healing difficulty, hand and limb deformity, and dislocation of hip joint, whole exome sequencing was used and revealed a compound heterozygous variant in NTRK1.MethodsDNA was extracted from peripheral blood samples of pediatric patients and their parents, and subjected to comprehensive analysis using whole-exome sequencing (WES), followed by verification of variant sites in the NTRK1 gene through Sanger sequencing. To elucidate the functional impact of the newly discovered variants, an in vitro experimental system was established. Splicing analysis was conducted using PCR and Sanger sequencing, while expression levels were assessed through qPCR and Western blot techniques.ResultsOne hotspot variant c.851-33T>A(ClinVar ID: 21308) and a novel variant c.850 + 5G>A(ClinVar ID:3069176) was inherited from her father and mother, respectively, identified in the affected individuals. The c.850 + 5G>A variant in NTRK1 resulted in two forms of aberrant mRNA splicing: 13bp deletion (c.838_850del13, p. Val280Ser fs180) and 25bp deletion (826_850del25, p. Val276Ser fs180) in exon 7, both leading to a translational termination at a premature stop codon and forming a C-terminal truncated protein. The expression of two abnormal splicing isoforms was decreased both in the level of mRNA and protein.ConclusionIn conclusion, this study elucidated the genetic cause of a patient with CIPA and identified a novel variant c.850 + 5G>A in NTRK1, which broadened the and enriched the NTRK1 mutation spectrum.

Congenital Insensitivity to Pain with Anhidrosis (CIPA): A Comprehensive Review

Abstract: Congenital Insensitivity to Pain with Anhidrosis (CIPA), also known as hereditary sensory and autonomic neuropathy type IV (HSAN IV), is a rare genetic disorder characterized by the inability to perceive pain and a lack of sweat (anhidrosis). This review aims to provide a comprehensive understanding of CIPA, including its clinical features, genetic basis, diagnostic challenges, and management strategies.

Trk-fused gene plays a critical role in diet-induced adipose tissue expansion and is also involved in thyroid hormone action.

Mutations in the Trk-fused gene (TFG) cause hereditary motor and sensory neuropathy with proximal dominant involvement, which reportedly has high co-incidences with diabetes and dyslipidemia, suggesting critical roles of the TFG in metabolism as well. We found that TFG expression levels in white adipose tissues (WATs) were elevated in both genetically and diet-induced obese mice and that TFG deletion in preadipocytes from the stromal vascular fraction (SVF) markedly inhibited adipogenesis. To investigate its role in vivo, we generated tamoxifen-inducible adipocyte-specific TFG knockout (AiTFG KO) mice. While a marked down-regulation of the peroxisome proliferator-activated receptor gamma target, de novo lipogenesis (DNL), and mitochondria-related gene expressions were observed in subcutaneous WAT (scWAT) from AiTFG KO mice, these effects were blunted in SVF-derived adipocytes when the TFG was deleted after differentiation into adipocytes, implying cell nonautonomous effects. Intriguingly, expressions of thyroid hormone receptors, as well as carbohydrate responsive element-binding protein β, which mediates the metabolic actions of thyroid hormone, were drastically down-regulated in scWAT from AiTFG KO mice. Reduced DNL and thermogenic gene expressions in AiTFG KO mice might be attributable to impaired thyroid hormone action in vivo. Finally, when adipocyte TFG was deleted in either the early or the late phase of high-fat diet feeding, the former brought about an impaired expansion of epididymal WAT, whereas the latter caused prominent adipocyte cell death. TFG deletion in adipocytes markedly exacerbated hepatic steatosis in both experimental settings. Collectively, these observations indicate that the TFG plays essential roles in maintaining normal adipocyte functions, including an enlargement of adipose tissue, thyroid hormone function, and thermogenic gene expressions, and in preserving hypertrophic adipocytes.

The pain target NaV1.7 is expressed late during human iPS cell differentiation into sensory neurons as determined in high-resolution imaging.

Human-induced pluripotent stem cells (iPS cells) are efficiently differentiated into sensory neurons. These cells express the voltage-gated sodium channel NaV1.7, which is a validated pain target. NaV1.7 deficiency leads to pain insensitivity, whereas NaV1.7 gain-of-function mutants are associated with chronic pain. During differentiation, the sensory neurons start spontaneous action potential firing around day 22, with increasing firing rate until day 40. Here, we used CRISPR/Cas9 genome editing to generate a HA-tag NaV1.7 to follow its expression during differentiation. We used two protocols to generate sensory neurons: the classical small molecule approach and a directed differentiation methodology and assessed surface NaV1.7 expression by Airyscan high-resolution microscopy. Our results show that maturation of at least 49days is necessary to observe robust NaV1.7 surface expression in both protocols. Electric activity of the sensory neurons precedes NaV1.7 surface expression. A clinically effective NaV1.7 blocker is still missing, and we expect this iPS cell model system to be useful for drug discovery and disease modeling.

Whole genome sequencing increases the diagnostic rate in Charcot-Marie-Tooth disease.

Charcot-Marie-Tooth disease (CMT) is one of the most common and genetically heterogeneous inherited neurological diseases, with more than 130 disease-causing genes. Whole genome sequencing (WGS) has improved diagnosis across genetic diseases, but the diagnostic impact in CMT is yet to be fully reported. We present the diagnostic results from a single specialist inherited neuropathy centre, including the impact of WGS diagnostic testing. Patients were assessed at our specialist inherited neuropathy centre from 2009-2023. Genetic testing was performed using single gene testing, next-generation sequencing targeted panels, research whole exome and whole genome sequencing (WGS), and latterly WGS through the UK National Health Service. Variants were assessed using the American College of Medical Genetics and Genomics and Association for Clinical Genomic Science criteria. Excluding patients with hereditary ATTR amyloidosis, 1515 patients with a clinical diagnosis of CMT and related disorders were recruited. 621 patients had CMT1 (41.0%), 294 CMT2 (19.4%), 205 intermediate CMT (CMTi, 13.5%), 139 hereditary motor neuropathy (HMN, 9.2%), 93 hereditary sensory neuropathy (HSN, 6.1%), 38 sensory ataxic neuropathy (2.5%), 72 hereditary neuropathy with liability to pressure palsies (HNPP, 4.8%) and 53 'complex' neuropathy (3.5%). Overall, a genetic diagnosis was reached in 76.9% (1165/1515). A diagnosis was most likely in CMT1 (96.8%, 601/621), followed by CMTi (81.0%, 166/205) and then HSN (69.9%, 65/93). Diagnostic rates remained less than 50% in CMT2, HMN and complex neuropathies. The most common genetic diagnosis was PMP22 duplication (CMT1A; 505/1165, 43.3%), then GJB1 (CMTX1; 151/1165, 13.0%), PMP22 deletion (HNPP; 72/1165, 6.2%) and MFN2 (CMT2A; 46/1165, 3.9%). We recruited 233 cases to the UK 100,000 Genomes Project (100KGP), of which 74 (31.8%) achieved a diagnosis; 28 had been otherwise diagnosed since recruitment leaving a true diagnostic rate of WGS through the 100KGP of 19.7% (46/233). However, almost half of the solved cases (35/74) received a negative report from the study, and the diagnosis was made through our research access to the WGS data. The overall diagnostic uplift of WGS for the entire cohort was 3.5%. Our diagnostic rate is the highest reported from a single centre, and has benefitted from the use of WGS, particularly access to the raw data. However, almost one quarter of all cases remain unsolved, and a new reference genome and novel technologies will be important to narrow the 'diagnostic gap'.

Damage to the esophagus in combination with hereditary motor and sensory neuropathy: description of a clinical case in a 12-year-old child

The article discusses a clinical case of a combination of achalasia of the cardia complicated by candidal esophagitis, which led to severe dysphagia and a significant decrease in body weight of a patient suffering from hereditary motor and sensory neuropathy - Charcot-Marie-Tooth disease (CMT) type 4 E. The authors highlight the pathogenesis and clinical picture diseases, features of the course of achalasia in a patient with a hereditary neurological disease. In this clinical case, an example of a disease in a 12-year-old girl is considered. A feature of this patient was progressive dysphagia, which ultimately led to the almost complete impossibility of normal food intake and the development of nutritional insufficiency. CMT disease is a heterogeneous group of hereditary disorders affecting the peripheral nervous system, as a result of the progression of the disease, motor and sensory dysfunction develops, such patients are under the supervision of neurologists. The presence of atypical symptoms, including not only progressive muscle weakness and exhaustion, with sensory deficits in the distal parts of the limbs, but also the severity of dysphagia, which from episodic becomes permanent, prevents the passage of not only solid food, but also liquid through the esophagus, the occurrence of esophageal vomiting - should serve as the basis for a complete examination of the patient using methods that allow visualization of the esophagus. In the available domestic literature, no description of the combined course of the pathological conditions indicated in the observation was found; isolated cases are given in the foreign literature, so the description of this clinical observation is relevant for raising awareness and early diagnosis of gastrointestinal smooth muscle dysfunction against the background of polyneuropathy.

Transient binocular vision loss and pain insensitivity in Klippel–Feil syndrome: a case report

BackgroundKlippel–Feil syndrome is a rare congenital bone disorder characterized by an abnormal fusion of two or more cervical spine vertebrae. Individuals with Klippel–Feil syndrome exhibit diverse clinical manifestations, including skeletal irregularities, visual and hearing impairments, orofacial anomalies, and anomalies in various internal organs, such as the heart, kidneys, genitourinary system, and nervous system.Case presentationThis case report describes a 12-year-old Pashtun female patient who presented with acute bilateral visual loss. The patient had Klippel–Feil syndrome, with the typical clinical triad symptoms of Klippel–Feil syndrome, along with Sprengel’s deformity. She also exhibited generalized hypoalgesia, which had previously resulted in widespread burn-related injuries. Upon examination, bilateral optic disc swelling was observed, but intracranial pressure was found to be normal. Extensive investigations yielded normal results, except for hypocalcemia and low vitamin D levels, while parathyroid function remained within the normal range. Visual acuity improved following 2 months of calcium and vitamin D supplementation, suggesting that the visual loss and optic nerve swelling were attributed to hypocalcemia. Given the normal parathyroid function, it is possible that hypocalcemia resulted from low vitamin D levels, which can occur after severe burn scarring. Furthermore, the patient received a provisional diagnosis of congenital insensitivity to pain on the basis of the detailed medical history and the findings of severe and widespread loss of the ability to perceive painful stimuli, as well as impaired temperature sensation. However, due to limitations in genetic testing, confirmation of the congenital insensitivity to pain diagnosis could not be obtained.ConclusionThis case highlights a rare presentation of transient binocular vision loss and pain insensitivity in a patient with Klippel–Feil syndrome, emphasizing the importance of considering unusual associations in symptom interpretation.

Syntaxin1A overexpression and pain insensitivity in individuals with 7q11.23 duplication syndrome.

Genetic modifications leading to pain insensitivity phenotypes, while rare, provide invaluable insights into the molecular biology of pain and reveal targets for analgesic drugs. Pain insensitivity typically results from Mendelian loss-of-function mutations in genes expressed in nociceptive (pain-sensing) dorsal root ganglion (DRG) neurons that connect the body to the spinal cord. We document a pain insensitivity mechanism arising from gene overexpression in individuals with the rare 7q11.23 duplication syndrome (Dup7), who have 3 copies of the approximately 1.5-megabase Williams syndrome (WS) critical region. Based on parental accounts and pain ratings, people with Dup7, mainly children in this study, are pain insensitive following serious injury to skin, bones, teeth, or viscera. In contrast, diploid siblings (2 copies of the WS critical region) and individuals with WS (1 copy) show standard reactions to painful events. A converging series of human assessments and cross-species cell biological and transcriptomic studies identified 1 likely candidate in the WS critical region, STX1A, as underlying the pain insensitivity phenotype. STX1A codes for the synaptic vesicle fusion protein syntaxin1A. Excess syntaxin1A was demonstrated to compromise neuropeptide exocytosis from nociceptive DRG neurons. Taken together, these data indicate a mechanism for producing "genetic analgesia" in Dup7 and offer previously untargeted routes to pain control.

In silico analyses of the involvement of GPR55, CB1R and TRPV1: response to THC, contribution to temporal lobe epilepsy, structural modeling and updated evolution.

The endocannabinoid (eCB) system is named after the discovery that endogenous cannabinoids bind to the same receptors as the phytochemical compounds found in Cannabis. While endogenous cannabinoids include anandamide (AEA) and 2-arachidonoylglycerol (2-AG), exogenous phytocannabinoids include Δ-9 tetrahydrocannabinol (THC) and cannabidiol (CBD). These compounds finely tune neurotransmission following synapse activation, via retrograde signaling that activates cannabinoid receptor 1 (CB1R) and/or transient receptor potential cation channel subfamily V member 1 (TRPV1). Recently, the eCB system has been linked to several neurological diseases, such as neuro-ocular abnormalities, pain insensitivity, migraine, epilepsy, addiction and neurodevelopmental disorders. In the current study, we aim to: (i) highlight a potential link between the eCB system and neurological disorders, (ii) assess if THC exposure alters the expression of eCB-related genes, and (iii) identify evolutionary-conserved residues in CB1R or TRPV1 in light of their function. To address this, we used several bioinformatic approaches, such as transcriptomic (Gene Expression Omnibus), protein-protein (STRING), phylogenic (BLASTP, MEGA) and structural (Phyre2, AutoDock, Vina, PyMol) analyzes. Using RNA sequencing datasets, we did not observe any dysregulation of eCB-related transcripts in major depressive disorders, bipolar disorder or schizophrenia in the anterior cingulate cortex, nucleus accumbens or dorsolateral striatum. Following in vivo THC exposure in adolescent mice, GPR55 was significantly upregulated in neurons from the ventral tegmental area, while other transcripts involved in the eCB system were not affected by THC exposure. Our results also suggest that THC likely induces neuroinflammation following in vitro application on mice microglia. Significant downregulation of TPRV1 occurred in the hippocampi of mice in which a model of temporal lobe epilepsy was induced, confirming previous observations. In addition, several transcriptomic dysregulations were observed in neurons of both epileptic mice and humans, which included transcripts involved in neuronal death. When scanning known interactions for transcripts involved in the eCB system (n = 12), we observed branching between the eCB system and neurophysiology, including proteins involved in the dopaminergic system. Our protein phylogenic analyzes revealed that CB1R forms a clade with CB2R, which is distinct from related paralogues such as sphingosine-1-phosphate, receptors, lysophosphatidic acid receptors and melanocortin receptors. As expected, several conserved residues were identified, which are crucial for CB1R receptor function. The anandamide-binding pocket seems to have appeared later in evolution. Similar results were observed for TRPV1, with conserved residues involved in receptor activation. The current study found that GPR55 is upregulated in neurons following THC exposure, while TRPV1 is downregulated in temporal lobe epilepsy. Caution is advised when interpreting the present results, as we have employed secondary analyzes. Common ancestors for CB1R and TRPV1 diverged from jawless vertebrates during the late Ordovician, 450 million years ago. Conserved residues are identified, which mediate crucial receptor functions.

Mitofusin 2 Variant Presenting With a Phenotype of Multiple System Atrophy of Cerebellar Subtype.

To investigate the etiology of cerebellar ataxia in an adult male patient. We performed standard neurologic assessment and genome sequencing of a 62-year-old man with rapidly progressive balance and gait abnormalities. The propositus exhibited cognitive dysfunction, mild appendicular bradykinesia, prominent appendicular ataxia, dysarthria, and hypomimia with minimal dysautonomic symptoms. Nerve conduction studies showed mild peripheral sensory neuropathy and normal motor nerve conduction velocities. Brain imaging showed progressive cerebellar atrophy and gliosis of the olivopontocerebellar fibers, characterized by T2 hyperintensity within the pons. Genetic testing revealed a likely pathogenic germline variant in MFN2 (NM_014874: c.[838C>T];[=], p.(R280C)) in the GTPase domain (G) interface; pathogenic variants of MFN2 typically cause hereditary sensory and motor neuropathy VI or Charcot-Marie-Tooth disease 2A. The presence of progressive ataxia, "hot cross bun" sign, and dysautonomia has been associated with multiple system atrophy, cerebellar type (MSA-C). We describe progressive cerebellar ataxia in an individual with a deleterious variant in MFN2. Our findings suggest that pathogenic variants in MFN2 can result in a spectrum of phenotypes including cerebellar ataxia with cerebellar-pontine atrophy in the absence of significant neuropathy and in a manner closely resembling MSA-C.

DNMT1 Y495C mutation interferes with maintenance methylation of imprinting control regions

Hereditary Sensory and Autonomic Neuropathy Type 1E (HSAN1E) is a rare autosomal dominant neurological disorder due to missense mutations in DNA methyltransferase 1 (DNMT1). To investigate the nature of the dominant effect, we compared methylomes of transgenic R1wtDnmt1 and R1Dnmt1Y495C mouse embryonic stem cells (mESCs) overexpressing WT and the mutant mouse proteins respectively, with the R1 (wild-type) cells. In case of R1Dnmt1Y495C, 15 out of the 20 imprinting control regions were hypomethylated with transcript level dysregulation of multiple imprinted genes in ESCs and neurons. Non-imprinted regions, minor satellites, major satellites, LINE1 and IAP repeats were unaffected. These data mirror the specific imprinting defects associated with transient removal of DNMT1 in mESCs, deletion of the maternal-effect DNMT1o variant in preimplantation mouse embryos, and in part, reprogramming to naïve human iPSCs. This is the first DNMT1 mutation demonstrated to specifically affect Imprinting Control Regions (ICRs), and reinforces the differences in maintenance methylation of ICRs over non-imprinted regions. Consistent with nervous system abnormalities in the HSAN1E disorder and involvement of imprinted genes in normal development and neurogenesis, R1Dnmt1Y495C cells showed dysregulated pluripotency and neuron marker genes, and yielded more slender, shorter, and extensively branched neurons. We speculate that R1Dnmt1Y495C cells produce predominantly dimers containing mutant proteins, leading to a gradual and specific loss of ICR methylation during early human development.

P14 Midface Toddler Excoriation Syndrome (MiTES): a new mimic of non-accidental injury

Abstract Background Midface Toddler Excoriation Syndrome (MiTES) is a rare genetic condition first described in 2017. Commencing in the first year of life, it is characterised by intense mid-­facial itch with persistent scratching and skin breakdown. Symptoms improve later in childhood, leaving atrophic scarring. Disbelief that infants can damage themselves in this way can lead to an erroneous and damaging misdiagnosis of non-accidental injury (NAI). Cases A boy now aged 11 years presented at 6 months with recurrent scratching of the face, leading to ulceration of the nasal bridge, sides of the nose, infraorbital areas and central forehead. Extensive investigations were unhelpful and NAI was suspected with significant psychosocial sequelae for the family. When his sister, now aged 4 years, presented with strikingly similar lesions MiTES was suspected and confirmed by genetic testing which showed homozygosity for 18 alanine repeats in the PRDM12 gene. Testing of sibling and parents is planned. Both children are now asymptomatic but have significant facial scarring. Discussion Biallelic variants in PRDM12 usually cause hereditary sensory and motor neuropathy type 8 with widespread damage to distal appendages due to pain insensitivity. The specific variant found here and in all reported MiTES cases causes highly localised lesions with rarely any extra-facial ­involvement. Due to its novelty and rarity, MiTES may be misdiagnosed and safeguarding concerns raised, leading to distress for affected families and breakdown of parent-­provider relationships. This case, which for the first time provides longitudinal data on affected siblings, highlights the need for early recognition and diagnosis.

The impact of sufferers' wealth status on pain perceptions: Its development and relation to allocation of healthcare resources.

Wealth-based disparities in health care wherein the poor receive undertreatment in painful conditions are a prominent issue that requires immediate attention. Research with adults suggests that these disparities are partly rooted in stereotypes associating poor individuals with pain insensitivity. However, whether and how children consider a sufferer's wealth status in their pain perceptions remains unknown. The present work addressed this question by testing 4- to 9-year-olds from the US and China. In Study 1 (N=108, 56 girls, 79% White), US participants saw rich and poor White children experiencing identical injuries and indicated who they thought felt more pain. Although 4- to 6-year-olds responded at chance, children aged seven and above attributed more pain to the poor than to the rich. Study 2 with a new sample of US children (N=111, 56 girls, 69% White) extended this effect to judgments of White adults' pain. Pain judgments also informed children's prosocial behaviors, leading them to provide medical resources to the poor. Studies 3 (N=118, 59 girls, 100% Asian) and 4 (N=80, 40 girls, 100% Asian) found that, when evaluating White and Asian people's suffering, Chinese children began to attribute more pain to the poor than to the rich earlier than US children. Thus, unlike US adults, US children and Chinese children recognize the poor's pain from early on. These findings add to our knowledge of group-based beliefs about pain sensitivity and have broad implications on ways to promote equitable health care. RESEARCH HIGHLIGHTS: Four studies examined whether 4- to 9-year-old children's pain perceptions were influenced by sufferers' wealth status. US children attributed more pain to White individuals of low wealth status than those of high wealth status by age seven. Chinese children demonstrated an earlier tendency to attribute more pain to the poor (versus the rich) compared to US children. Children's wealth-based pain judgments underlied their tendency to provide healthcare resources to people of low wealth status.

Mfsd7b facilitates choline transport and missense mutations affect choline transport function.

MFSD7b belongs to the Major Facilitator Superfamily of transporters that transport small molecules. Two isoforms of MFSD7b have been identified and they are reported to be heme exporters that play a crucial role in maintaining the cytosolic and mitochondrial heme levels, respectively. Mutations of MFSD7b (also known as FLVCR1) have been linked to retinitis pigmentosa, posterior column ataxia, and hereditary sensory and autonomic neuropathy. Although MFSD7b functions have been linked to heme detoxification by exporting excess heme from erythroid cells, it is ubiquitously expressed with a high level in the kidney, gastrointestinal tract, lungs, liver, and brain. Here, we showed that MFSD7b functions as a facilitative choline transporter. Expression of MFSD7b slightly but significantly increased choline import, while its knockdown reduced choline influx in mammalian cells. The influx of choline transported by MFSD7b is dependent on the expression of choline metabolizing enzymes such as choline kinase (CHKA) and intracellular choline levels, but it is independent ofgradient of cations. Additionally, we showed that choline transport function of Mfsd7b is conserved from fly to man. Employing our transport assays, we showed that missense mutations of MFSD7b caused reduced choline transport functions. Our results show that MFSD7b functions as a facilitative choline transporter in mammalian cells.

Upper and lower limb tremor in Charcot–Marie–Tooth neuropathy type 1A and the implications for standing balance

BackgroundNeuropathic tremor occurs in Charcot–Marie–Tooth neuropathy type 1A (CMT1A; hereditary motor and sensory neuropathy, HMSN), although the pathophysiological mechanisms remain to be elucidated. Separately, lower limb tremor has not been explored in CMT1A and could be associated with imbalance as in other neuropathies. The present study aimed to determine tremor characteristics in the upper and lower limbs in CMT1A and relate these findings to clinical disability, particularly imbalance.MethodsTremor and posturography studies were undertaken in phenotyped and genotyped CMT1A patients. Participants underwent detailed clinical assessment, tremor study recordings, and nerve conduction studies. Tremor stability index was calculated for upper limb tremor and compared to essential tremor.ResultsSeventeen patients were enrolled. Postural and kinetic upper limb tremors were evident in 65%, while postural and orthostatic lower limb tremors were seen in 35% of CMT1A patients. Peak upper limb frequencies were lower distally (~ 6 Hz) and higher proximally (~ 9 Hz), were unchanged by weight-loading, and not impacted by fatigue. The tremor stability index was significantly higher in CMT1A than in essential tremor. A 5–6 Hz lower limb tremor was recorded which did not vary along the limb and was unaffected by fatigue. Balance was impaired in patients with postural lower limb tremor. A high frequency peak on posturography was associated with ‘good’ balance.ConclusionsTremor is a common clinical feature in CMT1A, distinct from essential tremor, mediated by a complex interaction between peripheral and central mechanisms. Postural lower limb tremor is associated with imbalance; strategies aimed at tremor modulation could be of therapeutic utility.

Recurrent de novo SPTLC2 variant causes childhood-onset amyotrophic lateral sclerosis (ALS) by excess sphingolipid synthesis

BackgroundAmyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of the upper and lower motor neurons with varying ages of onset, progression and pathomechanisms. Monogenic childhood-onset ALS, although rare, forms an...

Novel TFG mutation causes autosomal-dominant spastic paraplegia and defects in autophagy

BackgroundMutations in the tropomyosin receptor kinase fused (TFG) gene are associated with various neurological disorders, including autosomal recessive hereditary spastic paraplegia (HSP), autosomal dominant hereditary motor and sensory neuropathy with...

Case report: Hereditary sensory autonomic neuropathy presenting as bifid deformity to the tongue

Hereditary sensory autonomic neuropathy (HSAN) is a group of rare genetic disorders in which affected patients have a diminished capacity to feel pain. Patients with HSAN may present with a wide range of factitial injuries, where injury to the oral cavity may be an early presenting sign. While existing literature on HSAN is scant, many reports highlight the long-term outcomes that may include enucleation of eyes, amputation of fingers and limbs, and disfigurement of the tongue. This case describes a five-month-old female with repetitive injury to the tongue causing it to heal with a bifid deformity. The patient was later diagnosed with HSAN type 4. This case highlights the importance of recognition of extensive oral trauma as one of the early signs of HSAN that should provoke a timely referral for neurological assessment.

Charcot-Marie-Tooth Disease with a Novel Variant in Gap Junction Protein Beta 1 Presenting with Visual Field Defects.

Pathogenic variants in Gap Junction Protein Beta 1 (GJB1) cause X-linked Charcot-Marie-Tooth (CMT) disease type 1 (CMTX1), which is a common hereditary motor and sensory neuropathy. A 45-year-old man presented with progressive muscle weakness, atrophy, sensory disturbance of all limbs from childhood, and visual field defects in both eyes at 40 years old. A segregation analysis revealed a novel variant, c.173C>A (p.P58H), in the GJB1 gene. Patients with variants at codon 58 in GJB1 showed clinically varied phenotypes, ranging from demyelinating neuropathy to cerebellar ataxia. This patient may represent one of the various clinical phenotypes of GJB1 variants.