Prevalence and Diagnostic Journey of Friedreich's Ataxia in the State of São Paulo, Brazil.

Friedreich's Ataxia (FRDA) is the leading cause of ataxia worldwide, but data on epidemiology and diagnostic journey are scarce, particularly in Latin America. Herein we estimated the prevalence of FRDA in the most populous Brazilian state and characterized the diagnostic odyssey of the disease. We received anonymized data of patients with FRDA from advocacy groups and physicians. Prevalence was estimated dividing the number of patients by the population of the state as reported in the last census. Patients were invited to answer an online survey to describe clinical data and diagnostic journey of the disease. FRDA estimated prevalence was 0.367:100,000, with a slight predominance of women (58.2% vs 41.7%). One hundred and four patients answered the survey (mean age of 37.3 ± 13.8 years; 75.9% classical and 24.0% late onset). On average, 6.2 ± 4.1 physicians were visited before reaching the diagnosis. Mean diagnostic delay was 7.8 ± 6.7 years; no difference between classical and LOFA groups was found. Most of the patients reported unsteadiness and gait abnormalities as the first symptom. Neurologists and orthopedical surgeons were the main specialties first sought by patients. We found a prevalence of 0.36:100,000 for FRDA in the state of São Paulo, Brazil. The disease is characterized by remarkable diagnostic delay, with no relevant differences between classical and LOFA patients.

Dominant NARS1 mutations causing axonal Charcot-Marie-Tooth disease expand NARS1-associated diseases.

Pathogenic variants in six aminoacyl-tRNA synthetase (ARS) genes are implicated in neurological disorders, most notably inherited peripheral neuropathies. ARSs are enzymes that charge tRNA molecules with cognate amino acids. Pathogenic variants in asparaginyl-tRNA synthetase (NARS1) cause a neurological phenotype combining developmental delay, ataxia and demyelinating peripheral neuropathy. NARS1 has not yet been linked to axonal Charcot-Marie-Tooth disease. Exome sequencing of patients with inherited peripheral neuropathies revealed three previously unreported heterozygous NARS1 variants in three families. Clinical and electrophysiological details were assessed. We further characterized all three variants in a yeast complementation model and used a knock-in mouse model to study variant p.Ser461Phe. All three variants (p.Met236del, p.Cys342Tyr and p.Ser461Phe) co-segregate with the sensorimotor axonal neuropathy phenotype. Yeast complementation assays show that none of the three NARS1 variants support wild-type yeast growth when tested in isolation (i.e. in the absence of a wild-type copy of NARS1), consistent with a loss-of-function effect. Similarly, the homozygous knock-in mouse model (p.Ser461Phe/Ser472Phe in mouse) also demonstrated loss-of-function characteristics. We present three previously unreported NARS1 variants segregating with a sensorimotor neuropathy phenotype in three families. Functional studies in yeast and mouse support variant pathogenicity. Thus, NARS1 is the seventh ARS implicated in dominant axonal Charcot-Marie-Tooth disease, further stressing that all dimeric ARSs should be evaluated for Charcot-Marie-Tooth disease.

Consensus from the Brazilian Academy of Neurology for the diagnosis, genetic counseling, and use of disease-modifying therapies in 5q spinal muscular atrophy.

Spinal muscular atrophy linked to chromosome 5 (SMA-5q) is an autosomal recessive genetic disease caused by mutations in the SMN1. SMA-5q is characterized by progressive degeneration of the spinal cord and bulbar motor neurons, causing severe motor and respiratory impairment with reduced survival, especially in its more severe clinical forms. In recent years, highly effective disease-modifying therapies have emerged, either acting by regulating the splicing of exon 7 of the SMN2 gene or adding a copy of the SMN1 gene through gene therapy, providing a drastic change in the natural history of the disease. In this way, developing therapeutic guides and expert consensus becomes essential to direct the use of these therapies in clinical practice. This consensus, prepared by Brazilian experts, aimed to review the main available disease-modifying therapies, critically analyze the results of clinical studies, and provide recommendations for their use in clinical practice for patients with SMA-5q. This consensus also addresses aspects related to diagnosis, genetic counseling, and follow-up of patients under drug treatment. Thus, this consensus provides valuable information regarding the current management of SMA-5q, helping therapeutic decisions in clinical practice and promoting additional gains in outcomes.

Atrofia muscular espinhal ligada ao cromossomo 5 (AME-5q) é uma doença genética de herança autossômica recessiva causada por mutações no gene SMN1. A AME-5q cursa com degeneração progressiva dos motoneurônios medulares e bulbares, acarretando grave comprometimento motor e respiratório com redução da sobrevida, especialmente nas suas formas clínicas mais graves. Nos últimos anos, terapias modificadoras da doença altamente eficazes, ou que atuam regulando o splicing do exon 7 do gene SMN2 ou adicionando uma cópia do gene SMN1 via terapia gênica, têm surgido, proporcionando uma mudança drástica na história natural da doença. Dessa forma, o desenvolvimento de guias terapêuticos e de consensos de especialistas torna-se importante no sentido de direcionar o uso dessas terapias na prática clínica. Este consenso, preparado por especialistas brasileiros, teve como objetivos revisar as principais terapias modificadoras de doença disponíveis, analisar criticamente os resultados dos estudos clínicos dessas terapias e prover recomendações para seu uso na prática clínica para pacientes com AME-5q. Aspectos relativos ao diagnóstico, aconselhamento genético e seguimento dos pacientes em uso das terapias também são abordados nesse consenso. Assim, esse consenso promove valiosas informações a respeito do manejo atual da AME-5q auxiliando decisões terapêuticas na prática clínica e promovendo ganhos adicionais nos desfechos finais.

Gene-based therapies for neuromuscular disorders.

Neuromuscular diseases (NMD) include a broad group of medical conditions with both acquired and genetic causes. In recent years, important advances have been made in the treatment of genetically caused NMD, and most of these advances are due to the implementation of therapies aimed at gene regulation. Among these therapies, gene replacement, small interfering RNA (siRNA), and antisense antinucleotides are the most promising approaches. More importantly, some of these therapies have already gained regulatory approval or are in the final stages of approval. The review focuses on motor neuron diseases, neuropathies, and Duchenne muscular dystrophy, summarizing the most recent developments in gene-based therapies for these conditions.

Doenças neuromusculares (DNM) compõem um grupo amplo de doenças de causa tanto adquiridas quanto genéticas. Nos últimos anos, importantes avanços ocorreram quanto ao tratamento das DNM de causa genética e grande parte desses avanços se deve à implementação de terapias voltadas para a modificação gênica. Dentre essas terapias, destacam-se as terapias de reposição gênica, uso de RNA de interferência, uso de antinucleotídeos antisense, entre outras. E, mais importante, algumas dessas terapias já se tornaram realidade na prática médica e já foram aprovadas, ou estão a poucos passos da aprovação, por órgãos governamentais regulatórios. Esta revisão aborda aspectos mais recentes quanto ao uso das terapias genéticas avançadas para algumas das formas mais comuns de DNM, em especial para doenças do neurônio motor (esclerose lateral amiotrófica e atrofia muscular espinhal), neuropatias e distrofia muscular de Duchenne.

Genetic diversity in hereditary axonal neuropathy: Analyzing 53 Brazilian children.

BACKGROUND AND AIMS: The genetic epidemiology of inherited neuropathies in children remains largely unknown. In this study, we specifically investigated the genetic profile of a Brazilian cohort of pediatric patients with pure or complex axonal neuropathies, a crucial knowledge in the near future for establishing treatment priorities and perspectives for this group of patients. METHODS: Fifty-three pediatric patients who were assessed prior to reaching the age of 20, and who had clinical diagnoses of axonal hereditary neuropathy or presented with axonal neuropathy as the primary clinical feature, were included in the study. The recruitment of these cases took place from January 1, 2018, to December 31, 2020. The diagnosis was based on clinical and electrophysiological data. A molecular assessment was made using target-gene panel or whole-exome sequencing. Subsequently, segregation analysis was performed on available family members, and all candidate variants found were confirmed through Sanger. RESULTS: A molecular diagnosis was reached in 68% of the patients (n = 36/53), considering only pathogenic and probably pathogenic variants. Variants in MFN2 (n = 15) and GJB1 (n = 3) accounted for half of the genetically confirmed patients (50%; n = 18/36). The other 18 genetically diagnosed patients had variants in several less common genes. INTERPRETATION: Apart from MFN2 and GJB1 genes, universally recognized as a frequent cause of axonal neuropathies in most studied population, our Brazilian cohort of children with axonal neuropathies showed an important genetic heterogeneity, probably reflecting the multi ethnicity of the Brazilian population. Diagnostic, counseling, and future interventions should consider this characteristic.

Cranial Nerve Thinning Distinguishes RFC1-Related Disorder from Other Late-Onset Ataxias.

BACKGROUND: RFC1-related disorder (RFC1/CANVAS) shares clinical features with other late-onset ataxias, such as spinocerebellar ataxias (SCA) and multiple system atrophy cerebellar type (MSA-C). Thinning of cranial nerves V (CNV) and VIII (CNVIII) has been reported in magnetic resonance imaging (MRI) scans of RFC1/CANVAS, but its specificity remains unclear. OBJECTIVES: To assess the usefulness of CNV and CNVIII thinning to differentiate RFC1/CANVAS from SCA and MSA-C. METHODS: Seventeen individuals with RFC1/CANVAS, 57 with SCA (types 2, 3 and 6), 11 with MSA-C and 15 healthy controls were enrolled. The Balanced Fast Field Echo sequence was used for assessment of cranial nerves. Images were reviewed by a neuroradiologist, who classified these nerves as atrophic or normal, and subsequently the CNV was segmented manually by an experienced neurologist. Both assessments were blinded to patient and clinical data. Non-parametric tests were used to assess between-group comparisons. RESULTS: Atrophy of CNV and CNVIII, both alone and in combination, was significantly more frequent in the RFC1/CANVAS group than in healthy controls and all other ataxia groups. Atrophy of CNV had the highest sensitivity (82%) and combined CNV and CNVIII atrophy had the best specificity (92%) for diagnosing RFC1/CANVAS. In the quantitative analyses, CNV was significantly thinner in the RFC1/CANVAS group relative to all other groups. The cutoff CNV diameter that best identified RFC1/CANVAS was ≤2.2 mm (AUC = 0.91; sensitivity 88.2%, specificity 95.6%). CONCLUSION: MRI evaluation of CNV and CNVIII using a dedicated sequence is an easy-to-use tool that helps to distinguish RFC1/CANVAS from SCA and MSA-C.

Role of the repeat expansion size in predicting age of onset and severity in RFC1 disease.

RFC1 disease, caused by biallelic repeat expansion in RFC1, is clinically heterogeneous in terms of age of onset, disease progression and phenotype. We investigated the role of the repeat size in influencing clinical variables in RFC1 disease. We also assessed the presence and role of meiotic and somatic instability of the repeat. In this study, we identified 553 patients carrying biallelic RFC1 expansions and measured the repeat expansion size in 392 cases. Pearson's coefficient was calculated to assess the correlation between the repeat size and age at disease onset. A Cox model with robust cluster standard errors was adopted to describe the effect of repeat size on age at disease onset, on age at onset of each individual symptoms, and on disease progression. A quasi-poisson regression model was used to analyse the relationship between phenotype and repeat size. We performed multi-variate linear regression to assess the association of the repeat size with the degree of cerebellar atrophy. Meiotic stability was assessed by Southern blotting on first-degree relatives of 27 probands. Finally, somatic instability was investigated by optical genome mapping on cerebellar and frontal cortex and unaffected peripheral tissue from four post-mortem cases. A larger repeat size of both smaller and larger allele was associated with an earlier age at neurological onset (smaller allele HR = 2.06, p < 0.001; larger allele HR = 1.53, p < 0.001) and with a higher hazard of developing disabling symptoms, such as dysarthria or dysphagia (smaller allele HR = 3.40, p < 0.001; larger allele HR = 1.71, p = 0.002) or loss of independent walking (smaller allele HR = 2.78, p < 0.001; larger allele HR = 1.60; p < 0.001) earlier in disease course. Patients with more complex phenotypes carried larger expansions (smaller allele: complex neuropathy RR = 1.30, p = 0.003; CANVAS RR = 1.34, p < 0.001; larger allele: complex neuropathy RR = 1.33, p = 0.008; CANVAS RR = 1.31, p = 0.009). Furthermore, larger repeat expansions in the smaller allele were associated with more pronounced cerebellar vermis atrophy (lobules I-V ß=-1.06, p < 0.001; lobules VI-VII ß=-0.34, p = 0.005). The repeat did not show significant instability during vertical transmission and across different tissues and brain regions. RFC1 repeat size, particularly of the smaller allele, is one of the determinants of variability in RFC1 disease and represents a key prognostic factor to predict disease onset, phenotype, and severity. Assessing the repeat size is warranted as part of the diagnostic test for RFC1 expansion.

Unveiling the clinical and electrophysiological profile of CMTX6: Insights from two Brazilian families.

BACKGROUND AND AIMS: X-linked Charcot-Marie-Tooth disease type 6 (CMTX6) is an extremely rare condition associated with mutations in the PDK3 gene. To date, only three families from different countries have been reported (Australia, South Korea, and Germany). In this study, we sought to provide a comprehensive clinical and electrophysiological characterization of two Brazilian families. METHODS: We conducted comprehensive clinical assessments, extensive electrophysiological evaluations, and performed whole-exome sequencing in the probands to investigate the genetic basis of the disease. RESULTS: Males in the family carrying the Arg162His mutation displayed early-onset motor and/or sensory axonal neuropathy, absence of tendon jerks, pes cavus, and frequently reported pain. Females in the same family exhibited a milder phenotype of the disease with later onset and some remained asymptomatic into their 50s. In the unrelated family with a single affected male, the clinical presentation was characterized by severe progressive sensorimotor polyneuropathy accompanied by neuropathic pain. INTERPRETATION: We report two Brazilian families with CMTX6 including one harboring a previously unpublished variant in the PDK3 gene, which co-segregates with the disease as expected in a X-linked disease. Notably, the clinical presentations across the five families with available descriptions, including our study, share striking similarities. Furthermore, the proximity of the three reported mutations suggests potential functional similarities and common underlying mechanisms. This study contributes to the growing knowledge of CMTX6 and underscores the importance of international collaborations in studying rare genetic disorders.

Genetic landscape of congenital insensitivity to pain and hereditary sensory and autonomic neuropathies.

Congenital insensitivity to pain (CIP) and hereditary sensory and autonomic neuropathies (HSAN) are clinically and genetically heterogeneous disorders exclusively or predominantly affecting the sensory and autonomic neurons. Due to the rarity of the diseases and findings based mainly on single case reports or small case series, knowledge about these disorders is limited. Here, we describe the molecular workup of a large international cohort of CIP/HSAN patients including patients from normally under-represented countries. We identify 80 previously unreported pathogenic or likely pathogenic variants in a total of 73 families in the >20 known CIP/HSAN-associated genes. The data expand the spectrum of disease-relevant alterations in CIP/HSAN, including novel variants in previously rarely recognized entities such as ATL3-, FLVCR1- and NGF-associated neuropathies and previously under-recognized mutation types such as larger deletions. In silico predictions, heterologous expression studies, segregation analyses and metabolic tests helped to overcome limitations of current variant classification schemes that often fail to categorize a variant as disease-related or benign. The study sheds light on the genetic causes and disease-relevant changes within individual genes in CIP/HSAN. This is becoming increasingly important with emerging clinical trials investigating subtype or gene-specific treatment strategies.

Eplontersen for Hereditary Transthyretin Amyloidosis With Polyneuropathy.

Importance: Transthyretin gene silencing is an emerging treatment strategy for hereditary transthyretin (ATTRv) amyloidosis. Objective: To evaluate eplontersen, an investigational ligand-conjugated antisense oligonucleotide, in ATTRv polyneuropathy. Design, Setting, and Participants: NEURO-TTRansform was an open-label, single-group, phase 3 trial conducted at 40 sites across 15 countries (December 2019-April 2023) in 168 adults with Coutinho stage 1 or 2 ATTRv polyneuropathy, Neuropathy Impairment Score 10-130, and a documented TTR variant. Patients treated with placebo from NEURO-TTR (NCT01737398; March 2013-November 2017), an inotersen trial with similar eligibility criteria and end points, served as a historical placebo ("placebo") group. Interventions: Subcutaneous eplontersen (45 mg every 4 weeks; n = 144); a small reference group received subcutaneous inotersen (300 mg weekly; n = 24); subcutaneous placebo weekly (in NEURO-TTR; n = 60). Main Outcomes and Measures: Primary efficacy end points at week 65/66 were changes from baseline in serum transthyretin concentration, modified Neuropathy Impairment Score +7 (mNIS+7) composite score (scoring range, -22.3 to 346.3; higher scores indicate poorer function), and Norfolk Quality of Life Questionnaire-Diabetic Neuropathy (Norfolk QoL-DN) total score (scoring range, -4 to 136; higher scores indicate poorer quality of life). Analyses of efficacy end points were based on a mixed-effects model with repeated measures adjusted by propensity score weights. Results: Among 144 eplontersen-treated patients (mean age, 53.0 years; 69% male), 136 (94.4%) completed week-66 follow-up; among 60 placebo patients (mean age, 59.5 years; 68% male), 52 (86.7%) completed week-66 follow-up. At week 65, adjusted mean percentage reduction in serum transthyretin was -81.7% with eplontersen and -11.2% with placebo (difference, -70.4% [95% CI, -75.2% to -65.7%]; P < .001). Adjusted mean change from baseline to week 66 was lower (better) with eplontersen vs placebo for mNIS+7 composite score (0.3 vs 25.1; difference, -24.8 [95% CI, -31.0 to -18.6; P < .001) and for Norfolk QoL-DN (-5.5 vs 14.2; difference, -19.7 [95% CI, -25.6 to -13.8]; P < .001). Adverse events by week 66 that led to study drug discontinuation occurred in 6 patients (4%) in the eplontersen group vs 2 (3%) in the placebo group. Through week 66, there were 2 deaths in the eplontersen group consistent with known disease-related sequelae (cardiac arrhythmia; intracerebral hemorrhage); there were no deaths in the placebo group. Conclusions and Relevance: In patients with ATTRv polyneuropathy, the eplontersen treatment group demonstrated changes consistent with significantly lowered serum transthyretin concentration, less neuropathy impairment, and better quality of life compared with a historical placebo. Trial Registration: ClinicalTrials.gov Identifier: NCT04136184; EU Clinical Trials Register: EudraCT 2019-001698-10.

Nigrostriatal dysfunction in RFC1-related disorder/CANVAS.

INTRODUCTION: Parkinsonism is now recognized as an additional feature in RFC1/CANVAS syndrome; however, no systematic evaluation of nigrostriatal dopaminergic function has been published so far. METHODS: This is an observational, single-center study, which analyzed 13 patients with molecular confirmation of RFC1/CANVAS. Disease severity was assessed with the SARA scale. Each subject was carefully evaluated for the presence of parkinsonian features. Dopamine transporter (DAT) imaging was acquired and reconstructed in the transverse, coronal and sagittal planes 4 h after venous injection of 99mTc-TRODAT-1. An experienced nuclear physician performed the visual analysis of all images. RESULTS: Patients had a mean age of 62.3 ± 8.8 years, and there were 9 women. The mean SARA score was 15.5 ± 5.8. Nine patients had abnormal DAT imaging results. The putamen was more frequently affected than the caudate nucleus on both sides. Considering all regions, uptake of 99mTc-TRODAT-1 did not correlate with disease duration or SARA scores. Parkinsonism was noticed in 3/13 patients, all of which had abnormal DAT scans. Interestingly, six subjects had reduced DAT imaging uptake, but no clinical signs of parkinsonism. CONCLUSION: Nigrostriatal dysfunction is frequent in RFC1/CANVAS even in the absence of clinical parkinsonism and may occur early in the disease course.

Frequency of GAA-FGF14 Ataxia in a Large Cohort of Brazilian Patients With Unsolved Adult-Onset Cerebellar Ataxia.

Objectives: Intronic FGF14 GAA repeat expansions have recently been found to be a common cause of hereditary ataxia (GAA-FGF14 ataxia; SCA27B). The global epidemiology and regional prevalence of this newly reported disorder remain to be established. In this study, we investigated the frequency of GAA-FGF14 ataxia in a large cohort of Brazilian patients with unsolved adult-onset ataxia. Methods: We recruited 93 index patients with genetically unsolved adult-onset ataxia despite extensive genetic investigation and genotyped the FGF14 repeat locus. Patients were recruited across 4 different regions of Brazil. Results: Of the 93 index patients, 8 (9%) carried an FGF14 (GAA)≥250 expansion. The expansion was also identified in 1 affected relative. Seven patients were of European descent, 1 was of African descent, and 1was of admixed American ancestry. One patient carrying a (GAA)376 expansion developed ataxia at age 28 years, confirming that GAA-FGF14 ataxia can occur before the age of 30 years. One patient displayed episodic symptoms, while none had downbeat nystagmus. Cerebellar atrophy was observed on brain MRI in 7 of 8 patients (87%). Discussion: Our results suggest that GAA-FGF14 ataxia is a common cause of adult-onset ataxia in the Brazilian population, although larger studies are needed to fully define its epidemiology.

Genetic Epidemiology and Clinical Characteristics of Patients with Spinocerebellar Ataxias in an Unexplored Brazilian State, Using Strategies for Resource-Limited Settings.

Spinocerebellar ataxias (SCAs) have a worldwide average prevalence of 2.7 cases per 100,000 individuals, with significant geographic variability. This study aimed to develop resource-limited strategies to detect and characterize the frequency and genetic-clinical profile of SCAs in an unexplored population from Alagoas State, a low Human Development Index state in northeastern Brazil. Active search strategies were employed to identify individuals with a diagnosis or clinical suspicion of SCAs, and a protocol for clinical and molecular evaluation was applied in collaboration with a reference center in Neurogenetics. A total of 73 individuals with SCAs were identified, with a minimum estimated prevalence of 2.17 cases per 100,000 inhabitants. SCA3 was the most common type (75.3%), followed by SCA7 (15.1%), SCA1 (6.8%), and SCA2 (2.7%). Patients with SCA3 subphenotype 2 were the most predominant. Detailed analysis of patients with SCA3 and SCA7 revealed age at onset and clinical features congruent with other studies, with gait disturbance and reduced visual capacity in SCA7 as the main initial manifestations. The study also identified many asymptomatic individuals at risk of developing SCAs. These findings demonstrate that simple and collaborative strategies can enhance the detection capacity of rare diseases such as SCAs in resource-limited settings and that Alagoas State has a minimum estimated prevalence of SCAs similar to the world average.

Morphological and morphometric study of the superior vestibular nerve trunk in guinea pigs.

The guinea pig has been chosen as a research model for otologic or neuropathic studies due to the relative ease of the cochlea, cochlear nerve, and vestibular nerve dissection. Little data have been reported on the normality of these nerves. The vestibular nerve is composed of the superior vestibular, inferior vestibular, and branch nerves. This study aimed to study the microscopic anatomy of the superior vestibular nerve (SVN) of guinea pigs using light microscopy and to search for normality patterns for use in experimental models in basic otologic research. We used eight male albino guinea pigs (Cavia porcellus, English strain), weighing between 400 and 500 g. After anesthetizing, the animals were perfused with a fixative solution of 2.5% glutaraldehyde. Dissection was performed by the access method to the temporal bone, coming to the rock and exposing the cochlea and vestibular nerve. The NVS fragments were removed, postfixed in osmium tetroxide, and embedded in the epoxy plastic resin Poly/Bed 812® (Polysciences Inc., Warrington, PA). Semi-thin transverse serial sections (0.5 µm) were made using a microtome MT6000-XL, RMC, Inc. and stained with toluidine blue. Morphology and morphometry were described and evaluated using the KS 400 application (Kontron 2.0, EchingBei, Munich, Germany) by macro, a computer program specially designed and developed for the study of the VIII nerve. The SVN was found to be devoid of epineurium, with only a thin conjunctive tissue layer. The myelin sheath of guinea pigs is relatively thin compared to the sensory and motor nerves found in mammals. The average fascicular area SVN was 0.19 ± 0.05 mm2 , with the largest area found to be 0.24 mm2 and the lowest was 0.12 mm2 . The average number of fibers was 5,753.00 ± 538 fibers. The density of myelinated fibers reached 32,316.08 ± 11,375.29 fibers/mm2 . Its diameter ranged from 1.0 to 9 µm and its peak was 3 µm. The measured results confirm the results of another study, indicating that the methodology is appropriate and reproducible. These findings are important for the evaluation of injured nerves in experimental models of peripheral neuropathy and basic ear disease.

Normal and pathogenic variation of RFC1 repeat expansions: implications for clinical diagnosis.

Cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS) is an autosomal recessive neurodegenerative disease, usually caused by biallelic AAGGG repeat expansions in RFC1. In this study, we leveraged whole genome sequencing data from nearly 10 000 individuals recruited within the Genomics England sequencing project to investigate the normal and pathogenic variation of the RFC1 repeat. We identified three novel repeat motifs, AGGGC (n = 6 from five families), AAGGC (n = 2 from one family) and AGAGG (n = 1), associated with CANVAS in the homozygous or compound heterozygous state with the common pathogenic AAGGG expansion. While AAAAG, AAAGGG and AAGAG expansions appear to be benign, we revealed a pathogenic role for large AAAGG repeat configuration expansions (n = 5). Long-read sequencing was used to characterize the entire repeat sequence, and six patients exhibited a pure AGGGC expansion, while the other patients presented complex motifs with AAGGG or AAAGG interruptions. All pathogenic motifs appeared to have arisen from a common haplotype and were predicted to form highly stable G quadruplexes, which have previously been demonstrated to affect gene transcription in other conditions. The assessment of these novel configurations is warranted in CANVAS patients with negative or inconclusive genetic testing. Particular attention should be paid to carriers of compound AAGGG/AAAGG expansions when the AAAGG motif is very large (>500 repeats) or the AAGGG motif is interrupted. Accurate sizing and full sequencing of the satellite repeat with long-read sequencing is recommended in clinically selected cases to enable accurate molecular diagnosis and counsel patients and their families.

Biallelic variants in COQ7 cause distal hereditary motor neuropathy with upper motor neuron signs.

COQ7 encodes a hydroxylase responsible for the penultimate step of coenzyme Q10 (CoQ10) biosynthesis in mitochondria. CoQ10 is essential for multiple cellular functions, including mitochondrial oxidative phosphorylation, lipid metabolism, and reactive oxygen species homeostasis. Mutations in COQ7 have been previously associated with primary CoQ10 deficiency, a clinically heterogeneous multisystemic mitochondrial disorder. We identified COQ7 biallelic variants in nine families diagnosed with distal hereditary motor neuropathy with upper neuron involvement, expending the clinical phenotype associated with defects in this gene. A recurrent p.Met1? change was identified in five families from Brazil with evidence of a founder effect. Fibroblasts isolated from patients revealed a substantial depletion of COQ7 protein levels, indicating protein instability leading to loss of enzyme function. High-performance liquid chromatography assay showed that fibroblasts from patients had reduced levels of CoQ10, and abnormal accumulation of the biosynthetic precursor DMQ10. Accordingly, fibroblasts from patients displayed significantly decreased oxygen consumption rates in patients, suggesting mitochondrial respiration deficiency. Induced pluripotent stem cell-derived motor neurons from patient fibroblasts showed significantly increased levels of extracellular neurofilament light protein, indicating axonal degeneration. Our findings indicate a molecular pathway involving CoQ10 biosynthesis deficiency and mitochondrial dysfunction in patients with distal hereditary motor neuropathy. Further studies will be important to evaluate the potential benefits of CoQ10 supplementation in the clinical outcome of the disease.

Brazilian consensus for diagnosis, management and treatment of hereditary transthyretin amyloidosis with peripheral neuropathy: second edition.

Hereditary transthyretin amyloidosis with peripheral neuropathy (ATTRv-PN) is an autosomal dominant inherited sensorimotor and autonomic polyneuropathy with over 130 pathogenic variants identified in the TTR gene. Hereditary transthyretin amyloidosis with peripheral neuropathy is a disabling, progressive and life-threatening genetic condition that leads to death in ∼ 10 years if untreated. The prospects for ATTRv-PN have changed in the last decades, as it has become a treatable neuropathy. In addition to liver transplantation, initiated in 1990, there are now at least 3 drugs approved in many countries, including Brazil, and many more are being developed. The first Brazilian consensus on ATTRv-PN was held in the city of Fortaleza, Brazil, in June 2017. Given the new advances in the area over the last 5 years, the Peripheral Neuropathy Scientific Department of the Brazilian Academy of Neurology organized a second edition of the consensus. Each panelist was responsible for reviewing the literature and updating a section of the previous paper. Thereafter, the 18 panelists got together virtually after careful review of the draft, discussed each section of the text, and reached a consensus for the final version of the manuscript.

Polineuropatia amiloidótica familiar associada a transtirretina (ATTRv-PN) é uma polineuropatia sensitivo-motora e autonômica hereditária autossômica dominante com mais de 130 variantes patogênicas já identificadas no gene TTR. A ATTRv-PN é uma condição genética debilitante, progressiva e que ameaça a vida, levando à morte em ∼ 10 anos se não for tratada. Nas últimas décadas, a ATTRv-PN se tornou uma neuropatia tratável. Além do transplante de fígado, iniciado em 1990, temos agora 3 medicamentos modificadores de doença aprovados em muitos países, incluindo o Brasil, e muitas outras medicações estão em desenvolvimento. O primeiro consenso brasileiro em ATTRv-PN foi realizado em Fortaleza em junho de 2017. Devido aos novos avanços nesta área nos últimos 5 anos, o Departamento Científico de Neuropatias Periféricas da Academia Brasileira de Neurologia organizou uma segunda edição do consenso. Cada panelista ficou responsável por rever a literatura e atualizar uma parte do manuscrito. Finalmente, os 18 panelistas se reuniram virtualmente após revisão da primeira versão, discutiram cada parte do artigo e chegaram a um consenso sobre a versão final do manuscrito.

DNA methylation in regulatory elements of the FKBP5 and NR3C1 gene in mother-child binomials with depression.

BACKGROUND: The FKBP5 and NR3C1 genes play an important role in stress response, thus impacting mental health. Stress factor exposure in early life, such as maternal depression, may contribute to epigenetic modifications in stress response genes, increasing the susceptibility to different psychopathologies. The present study aimed to evaluate the DNA methylation profile in maternal-infant depression in regulatory regions of the FKBP5 gene and the alternative promoter of the NR3C1 gene. METHODS: We evaluated 60 mother-infant pairs. The levels of DNA methylation were analyzed by the MSRED-qPCR technique. RESULTS: We observed an increased DNA methylation profile in the NR3C1 gene promoter in children with depression and children exposed to maternal depression (p < 0.05). In addition, we observed a correlation of DNA methylation between mothers and offspring exposed to maternal depression. This correlation shows a possible intergenerational effect of maternal MDD exposure on the offspring. For FKBP5, we found a decrease in DNA methylation at intron 7 in children exposed to maternal MDD during pregnancy and a correlation of DNA methylation between mothers and children exposed to maternal MDD (p < 0.05). LIMITATIONS: Although the individuals of this study are a rare group, the sample size of the study was small, and we evaluated the DNA methylation of only one CpG site for each region. CONCLUSION: These results indicate changes in DNA methylation levels in regulatory regions of FKBP5 and NR3C1 in the mother-child MDD context and represent a potential target of studies to understand the depression etiology and how it occurs between generations.

Inter-rater reliability of the Rasch-modified medical research council scoring criteria for manual muscle testing in neuromuscular diseases.

It was argued that researchers and clinicians are not able to make judgments between most categories of the original Medical Research Council (MRC) scale and that a modified short version would reach higher agreement levels. We aimed to assess the inter-rater reliability for both the original and the Rasch-modified MRC scoring criteria of Manual Muscle Strength tests (MMSt) in patients with neuromuscular diseases. Two MRC scoring criteria were used to score muscle strength using MMSt in 40 muscle groups of the upper and lower limbs in patients with neuromuscular disorders. Three investigators performed the evaluations; the order of the MMSt and the use of the scales were performed according to the preferences of the investigators. The agreement coefficient (Gwet's AC2 ) was used to compute the reliability. Sixty patients (mean age of 39.3 years ± 15.2) with neuromuscular diseases were included. The mean AC2 for the muscle groups of the upper limbs ranged from 0.82 to 0.96 using the modified MRC scale and from 0.86 to 0.96 using the original MRC scale. The AC2 for the lower limb muscle groups ranged from 0.80 to 0.91 (modified MRC scale) and from 0.87 to 0.93 (original MRC scale). These values might be interpreted as "almost perfect agreement" with no significant differences between the scales. The results indicate that both MRC scoring criteria have significant reliability among trained observers. Moreover, the Rasch-modified MRC scale is as reliable as the original MRC scale and can be used in future clinical studies.

An Exploratory Survey on the Care for Ataxic Patients in the American Continents and the Caribbean.

Little is known about access of rare disease carriers to health care. To increase this knowledge, the Pan American Hereditary Ataxia Network (PAHAN) conducted an exploratory survey about care for hereditary ataxias in American continents and the Caribbean. A questionnaire was sent to health professionals about the hereditary ataxias identified; access to care; and local teaching and research. The number of ataxics under current care per 100,000 inhabitants was subtracted from the expected overall prevalence of 6/100,000, to estimate the prevalence of uncovered ataxic patients. Local Human Development Indexes (HDI) were used to measure socio-economic factors. Twenty-six sites participated. Twelve sites had very high, 13 had high, and one site had medium HDI. Participants reported on 2239 and 602 patients with spinocerebellar ataxias and recessive forms under current care. The number of patients under current care per inhabitants varied between 0.14 and 12/100,000. The estimated prevalence of uncovered ataxic patients was inversely proportional to HDIs (rho = 0.665, p = 0.003). Access to diagnosis, pre-symptomatic tests, and rehabilitation were associated with HDIs. More and better molecular diagnostic tools, protocols and guidelines, and professional training for ataxia care were the top priorities common to all respondents. Evidence of inequalities was confirmed. Lower HDIs were associated with high potential numbers of uncovered ataxic subjects, and with lack of molecular diagnosis, pre-symptomatic testing, and rehabilitation. More and better diagnostic tools, guidelines, and professional training were priorities to all sites. PAHAN consortium might help with the last two tasks.