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PURPOSE: To evaluate the diagnostic utility of publicly funded clinical exome sequencing (ES) for patients with suspected rare genetic diseases. METHODS: We prospectively enrolled 297 probands who met eligibility criteria and received ES across 5 sites in Ontario, Canada, and extracted data from medical records and clinician surveys. Using the Fryback and Thornbury Efficacy Framework, we assessed diagnostic accuracy by examining laboratory interpretation of results and assessed diagnostic thinking by examining the clinical interpretation of results and whether clinical-molecular diagnoses would have been achieved via alternative hypothetical molecular tests. RESULTS: Laboratories reported 105 molecular diagnoses and 165 uncertain results in known and novel genes. Of these, clinicians interpreted 102 of 105 (97%) molecular diagnoses and 6 of 165 (4%) uncertain results as clinical-molecular diagnoses. The 108 clinical-molecular diagnoses were in 104 families (35% diagnostic yield). Each eligibility criteria resulted in diagnostic yields of 30% to 40%, and higher yields were achieved when >2 eligibility criteria were met (up to 45%). Hypothetical tests would have identified 61% of clinical-molecular diagnoses. CONCLUSION: We demonstrate robustness in eligibility criteria and high clinical validity of laboratory results from ES testing. The importance of ES was highlighted by the potential 40% of patients that would have gone undiagnosed without this test.
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Exoma , Doenças Raras , Humanos , Estudos Prospectivos , Sequenciamento do Exoma , Doenças Raras/diagnóstico , Doenças Raras/genética , Testes Genéticos/métodos , OntárioRESUMO
Status dystonicus is the most severe form of dystonia with life-threatening complications if not treated promptly. We present consensus recommendations for the initial management of acutely worsening dystonia (including pre-status dystonicus and status dystonicus), as well as refractory status dystonicus in children. This guideline provides a stepwise approach to assessment, triage, interdisciplinary treatment, and monitoring of status dystonicus. The clinical pathways aim to: (1) facilitate timely recognition/triage of worsening dystonia, (2) standardize supportive and dystonia-directed therapies, (3) provide structure for interdisciplinary cooperation, (4) integrate advances in genomics and neuromodulation, (5) enable multicenter quality improvement and research, and (6) improve outcomes. © 2024 International Parkinson and Movement Disorder Society.
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OBJECTIVES: We aimed to explore the prevalence of peroneal neuropathy in children during coronavirus disease-19 (COVID-19) pandemic. BACKGROUND: Since the COVID-19 outbreak, many children worldwide have experienced a dramatic lifestyle changes, including conducting most daily activities indoors. Peroneal nerve palsy is one of the most common entrapment neuropathies and circumstances as prolonged immobilization or leg crossing predisposes an individual to peroneal neuropathy. METHODS: This is a case-control retrospective study that included patients referred to our neurophysiology clinic with foot drop. We compared the prevalence of spontaneous peroneal neuropathy 1 year before (April 2019/March 2020) and 1 year during the COVID-19 pandemic (April 2020/March 2021); and we also continued collecting data prospectively between April and September 2021 analysis the whole pandemic period. RESULTS: Totally, 399 patient clinical notes and NCS/EMG reports were reviewed, 220 were evaluated 1 year before and 179 1 year during COVID-19 pandemic. During the COVID-19 pandemic, there was a higher prevalence of peroneal neuropathy (odds ratio 4.74, 95%CI 1.30-17.25, p = 0.0183). In the COVID group (n = 11), mean age was 14 years and 63.4% were males. Mean age was 15 years and 66.7% were males in the Control group (n = 3). There was a significant difference in the time from symptoms onset to the neurophysiology assessment, with a mean time of 14 days in the Control group and 87.5 days in the COVID group. CONCLUSIONS: This study provides evidence that during the COVID-19 pandemic period, there was a higher prevalence of peroneal neuropathy among children. Strategies to prevent peroneal neuropathy should be recommened to this age group.
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COVID-19 , Neuropatias Fibulares , Masculino , Humanos , Criança , Adolescente , Feminino , Neuropatias Fibulares/epidemiologia , Neuropatias Fibulares/diagnóstico , Pandemias , Estudos Retrospectivos , Prevalência , COVID-19/epidemiologiaRESUMO
Gene-panel and whole-exome analyses are now standard methodologies for mutation detection in Mendelian disease. However, the diagnostic yield achieved is at best 50%, leaving the genetic basis for disease unsolved in many individuals. New approaches are thus needed to narrow the diagnostic gap. Whole-genome sequencing is one potential strategy, but it currently has variant-interpretation challenges, particularly for non-coding changes. In this study we focus on transcriptome analysis, specifically total RNA sequencing (RNA-seq), by using monogenetic neuromuscular disorders as proof of principle. We examined a cohort of 25 exome and/or panel "negative" cases and provided genetic resolution in 36% (9/25). Causative mutations were identified in coding and non-coding exons, as well as in intronic regions, and the mutational pathomechanisms included transcriptional repression, exon skipping, and intron inclusion. We address a key barrier of transcriptome-based diagnostics: the need for source material with disease-representative expression patterns. We establish that blood-based RNA-seq is not adequate for neuromuscular diagnostics, whereas myotubes generated by transdifferentiation from an individual's fibroblasts accurately reflect the muscle transcriptome and faithfully reveal disease-causing mutations. Our work confirms that RNA-seq can greatly improve diagnostic yield in genetically unresolved cases of Mendelian disease, defines strengths and challenges of the technology, and demonstrates the suitability of cell models for RNA-based diagnostics. Our data set the stage for development of RNA-seq as a powerful clinical diagnostic tool that can be applied to the large population of individuals with undiagnosed, rare diseases and provide a framework for establishing minimally invasive strategies for doing so.
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Marcadores Genéticos , Variação Genética , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Doenças Musculares/diagnóstico , Mutação , Doenças Raras/diagnóstico , Adolescente , Adulto , Células Cultivadas , Criança , Estudos de Coortes , Feminino , Humanos , Masculino , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/patologia , Doenças Musculares/genética , Doenças Raras/genética , Transcriptoma , Adulto JovemRESUMO
BACKGROUND: Spinal muscular atrophy (SMA) is characterized by the progressive loss of motor neurons causing muscle atrophy and weakness. Nusinersen, the first effective SMA therapy was approved by Health Canada in June 2017 and has been added to the provincial formulary of all but one Canadian province. Access to this effective therapy has triggered the inclusion of SMA in an increasing number of Newborn Screening (NBS) programs. However, the range of disease-modifying SMN2 gene copy numbers encountered in survival motor neuron 1 (SMN1)-null individuals means that neither screen-positive definition nor resulting treatment decisions can be determined by SMN1 genotype alone. We outline an approach to this challenge, one that specifically addresses the case of SMA newborns with four copies of SMN2. OBJECTIVES: To develop a standardized post-referral evaluation pathway for babies with a positive SMA NBS screen result. METHODS: An SMA NBS pilot trial in Ontario using first-tier MassARRAY and second-tier multi-ligand probe amplification (MLPA) was launched in January 2020. Prior to this, Ontario pediatric neuromuscular disease and NBS experts met to review the evidence regarding the diagnosis and treatment of children with SMA as it pertained to NBS. A post-referral evaluation algorithm was developed, outlining timelines for patient retrieval and management. CONCLUSIONS: Ontario's pilot NBS program has created a standardized path to facilitate early diagnosis of SMA and initiation of treatment. The goal is to provide timely access to those SMA infants in need of therapy to optimize motor function and prolong survival.
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Atrofia Muscular Espinal , Triagem Neonatal , Diagnóstico Precoce , Seguimentos , Humanos , Recém-Nascido , OntárioRESUMO
PURPOSE: Deep brain stimulation (DBS) is a common tool for the treatment of movement disorders in adults; however, it remains an emerging treatment modality in children with a growing number of indications, including epilepsy and dystonia. The Child & Youth CompreHensIve Longitudinal Database of DBS (CHILD-DBS) study aims to prospectively collect relevant data on quality of life (QoL), safety, efficacy, and long-term neurodevelopmental outcomes following DBS in children. METHODS: Data are collected and managed using the Research Electronic Data Capture (REDCap). This database aims to collect multicentre comprehensive and longitudinal clinical, QoL, imaging and electrophysiologic data for children under the age of 19 undergoing DBS. RESULTS: Both general and indication-specific measures are collected at baseline and at four time points postoperatively: 6 months, 1 year, 2 years, and 3 years. The database encompasses QoL metrics for children, including the PedsQL (Pediatric Quality of Life Inventory, generic), QOLCE (Quality of Life in Childhood Epilepsy Questionnaire, parent-rated), CHU 9D (Child Health Utility 9D), and KIDSCREEN. Caregiver clinical and QoL metrics, including QIDS (Quick Inventory of Depressive Symptomatology), GAD-7 (Generalized Anxiety Disorder 7-item scale), and CarerQoL-7D (The Care-related Quality of Life Instrument), are similarly prospectively collected. Healthcare resource utilization is also assessed before and after DBS. Lastly, stimulation parameters and radiographic and electrophysiologic data are collected within the database. CONCLUSIONS: The development of the current prospective paediatric DBS database with carefully selected physical and psychosocial outcomes and assessments will complement existing efforts to enhance and facilitate multisite collaboration to further understand the role of DBS in childhood.
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Estimulação Encefálica Profunda , Distonia , Distúrbios Distônicos , Adolescente , Adulto , Criança , Distúrbios Distônicos/terapia , Humanos , Qualidade de Vida , Resultado do TratamentoRESUMO
BACKGROUND: Spinal muscular atrophy (SMA) is a devastating rare disease that affects individuals regardless of ethnicity, gender, and age. The first-approved disease-modifying therapy for SMA, nusinursen, was approved by Health Canada, as well as by American and European regulatory agencies following positive clinical trial outcomes. The trials were conducted in a narrow pediatric population defined by age, severity, and genotype. Broad approval of therapy necessitates close follow-up of potential rare adverse events and effectiveness in the larger real-world population. METHODS: The Canadian Neuromuscular Disease Registry (CNDR) undertook an iterative multi-stakeholder process to expand the existing SMA dataset to capture items relevant to patient outcomes in a post-marketing environment. The CNDR SMA expanded registry is a longitudinal, prospective, observational study of patients with SMA in Canada designed to evaluate the safety and effectiveness of novel therapies and provide practical information unattainable in trials. RESULTS: The consensus expanded dataset includes items that address therapy effectiveness and safety and is collected in a multicenter, prospective, observational study, including SMA patients regardless of therapeutic status. The expanded dataset is aligned with global datasets to facilitate collaboration. Additionally, consensus dataset development aimed to standardize appropriate outcome measures across the network and broader Canadian community. Prospective outcome studies, data use, and analyses are independent of the funding partner. CONCLUSION: Prospective outcome data collected will provide results on safety and effectiveness in a post-therapy approval era. These data are essential to inform improvements in care and access to therapy for all SMA patients.
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Atrofia Muscular Espinal , Canadá , Criança , Humanos , Atrofia Muscular Espinal/terapia , Estudos Prospectivos , Doenças Raras , Sistema de RegistrosRESUMO
Clustered regularly interspaced short palindromic repeat (CRISPR) has arisen as a frontrunner for efficient genome engineering. However, the potentially broad therapeutic implications are largely unexplored. Here, to investigate the therapeutic potential of CRISPR/Cas9 in a diverse set of genetic disorders, we establish a pipeline that uses readily obtainable cells from affected individuals. We show that an adapted version of CRISPR/Cas9 increases the amount of utrophin, a known disease modifier in Duchenne muscular dystrophy (DMD). Furthermore, we demonstrate preferential elimination of the dominant-negative FGFR3 c.1138G>A allele in fibroblasts of an individual affected by achondroplasia. Using a previously undescribed approach involving single guide RNA, we successfully removed large genome rearrangement in primary cells of an individual with an X chromosome duplication including MECP2. Moreover, removal of a duplication of DMD exons 18-30 in myotubes of an individual affected by DMD produced full-length dystrophin. Our findings establish the far-reaching therapeutic utility of CRISPR/Cas9, which can be tailored to target numerous inherited disorders.
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Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Doenças Genéticas Inatas/terapia , Alelos , Expressão Gênica , Doenças Genéticas Inatas/genética , Humanos , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/terapiaRESUMO
Pediatric neuromuscular diseases encompass all disorders with onset in childhood and where the primary area of pathology is in the peripheral nervous system. These conditions are largely genetic in etiology, and only those with a genetic underpinning will be presented in this review. This includes disorders of the anterior horn cell (e.g., spinal muscular atrophy), peripheral nerve (e.g., Charcot-Marie-Tooth disease), the neuromuscular junction (e.g., congenital myasthenic syndrome), and the muscle (myopathies and muscular dystrophies). Historically, pediatric neuromuscular disorders have uniformly been considered to be without treatment possibilities and to have dire prognoses. This perception has gradually changed, starting in part with the discovery and widespread application of corticosteroids for Duchenne muscular dystrophy. At present, several exciting therapeutic avenues are under investigation for a range of conditions, offering the potential for significant improvements in patient morbidities and mortality and, in some cases, curative intervention. In this review, we will present the current state of treatment for the most common pediatric neuromuscular conditions, and detail the treatment strategies with the greatest potential for helping with these devastating diseases.
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Doenças Neuromusculares/terapia , Fatores Etários , Animais , Ensaios Clínicos como Assunto , Terapia Combinada/métodos , Gerenciamento Clínico , Humanos , Doenças Neuromusculares/diagnóstico , Doenças Neuromusculares/etiologia , PediatriaRESUMO
Muscle contraction upon nerve stimulation relies on excitation-contraction coupling (ECC) to promote the rapid and generalized release of calcium within myofibers. In skeletal muscle, ECC is performed by the direct coupling of a voltage-gated L-type Ca2+ channel (dihydropyridine receptor; DHPR) located on the T-tubule with a Ca2+ release channel (ryanodine receptor; RYR1) on the sarcoplasmic reticulum (SR) component of the triad. Here, we characterize a novel class of congenital myopathy at the morphological, molecular, and functional levels. We describe a cohort of 11 patients from 7 families presenting with perinatal hypotonia, severe axial and generalized weakness. Ophthalmoplegia is present in four patients. The analysis of muscle biopsies demonstrated a characteristic intermyofibrillar network due to SR dilatation, internal nuclei, and areas of myofibrillar disorganization in some samples. Exome sequencing revealed ten recessive or dominant mutations in CACNA1S (Cav1.1), the pore-forming subunit of DHPR in skeletal muscle. Both recessive and dominant mutations correlated with a consistent phenotype, a decrease in protein level, and with a major impairment of Ca2+ release induced by depolarization in cultured myotubes. While dominant CACNA1S mutations were previously linked to malignant hyperthermia susceptibility or hypokalemic periodic paralysis, our findings strengthen the importance of DHPR for perinatal muscle function in human. These data also highlight CACNA1S and ECC as therapeutic targets for the development of treatments that may be facilitated by the previous knowledge accumulated on DHPR.
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Canais de Cálcio/genética , Canais de Cálcio/metabolismo , Miotonia Congênita/genética , Miotonia Congênita/metabolismo , Adolescente , Adulto , Cálcio/metabolismo , Canais de Cálcio Tipo L , Células Cultivadas , Criança , Estudos de Coortes , Família , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Células Musculares/metabolismo , Células Musculares/patologia , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Mutação , Miotonia Congênita/diagnóstico por imagem , Miotonia Congênita/patologia , Fenótipo , Homologia de Sequência de Aminoácidos , Adulto JovemRESUMO
Centronuclear myopathies are congenital muscle disorders characterized by type I myofibre predominance and an increased number of muscle fibres with nuclear centralization. The severe neonatal X-linked form is due to mutations in MTM1, autosomal recessive centronuclear myopathy with neonatal or childhood onset results from mutations in BIN1 (amphiphysin 2), and dominant cases were previously associated to mutations in DNM2 (dynamin 2). Our aim was to determine the genetic basis and physiopathology of patients with mild dominant centronuclear myopathy without mutations in DNM2. We hence established and characterized a homogeneous cohort of nine patients from five families with a progressive adult-onset centronuclear myopathy without facial weakness, including three sporadic cases and two families with dominant disease inheritance. All patients had similar histological and ultrastructural features involving type I fibre predominance and hypotrophy, as well as prominent nuclear centralization and clustering. We identified heterozygous BIN1 mutations in all patients and the molecular diagnosis was complemented by functional analyses. Two mutations in the N-terminal amphipathic helix strongly decreased the membrane-deforming properties of amphiphysin 2 and three stop-loss mutations resulted in a stable protein containing 52 supernumerary amino acids. Immunolabelling experiments revealed abnormal central accumulation of dynamin 2, caveolin-3, and the autophagic marker p62, and general membrane alterations of the triad, the sarcolemma, and the basal lamina as potential pathological mechanisms. In conclusion, we identified BIN1 as the second gene for dominant centronuclear myopathy. Our data provide the evidence that specific BIN1 mutations can cause either recessive or dominant centronuclear myopathy and that both disorders involve different pathomechanisms.
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Proteínas Adaptadoras de Transdução de Sinal/genética , Mutação/genética , Miopatias Congênitas Estruturais/genética , Proteínas Nucleares/genética , Proteínas Supressoras de Tumor/genética , Adulto , Idade de Início , Dinamina II/genética , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/metabolismoRESUMO
LAMB2 gene disorders present with different phenotypes. Pierson syndrome (PS) is a common phenotype associated with LAMB2 variants. Neuromuscular phenotype has been reported including hypotonia and developmental delay. However, neuromuscular junction abnormalities represented as congenital myasthenic syndrome (CMS) was reported in one adult patient only. Here, in this paper, we present two pediatric cases with a severe presentation of PS and have CMS so expanding the knowledge of LAMB2 related phenotypes. The first patient had hypotonia and global developmental delay. Targeted genetic testing panel demonstrated homozygous pathogenic variant in the LAMB2 gene (c.5182C>T, pGln1728*) which was reported by Maselli et al. 2009. Repetitive nerve stimulation (RNS) showed a decremental response at low frequency of 3 Hz. On the other hand, the second patient had profound weakness since birth. Tri-Whole exome sequencing showed homozygous pathogenic variant in the LAMB2 gene c.2890C>T, pArg964*. A trial of salbutamol did not improve the symptoms. Both patients passed away from sequala of PS. The spectrum of phenotypic changes associated with LAMB2 mutations is still expanding, and further investigation into the various clinical and morphologic presentations associated with these mutations is important to better identify and manage affected individuals.
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Síndromes Miastênicas Congênitas , Humanos , Síndromes Miastênicas Congênitas/genética , Síndromes Miastênicas Congênitas/fisiopatologia , Síndromes Miastênicas Congênitas/diagnóstico , Masculino , Feminino , Anormalidades do Olho/genética , Anormalidades do Olho/complicações , Laminina/genética , Fenótipo , Mutação , Anormalidades Múltiplas/genética , Lactente , Doenças da Junção Neuromuscular/genética , Pré-Escolar , Síndrome Nefrótica , Distúrbios PupilaresRESUMO
Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare autoimmune neurological disorder seen in both pediatric and adult populations. CIDP typically presents with progressive and persistent weakness over at least 4 weeks in addition to sensory symptoms in the extremities. Although CIDP shares common clinical features between children and adults, it sometimes presents as a distinct clinical entity in children that requires close attention and recognition. A major caveat when diagnosing a child with CIDP is the clinical and diagnostic overlap with inherited neuropathies, most commonly Charcot-Marie-Tooth disease (CMT). Demyelinating CMT (dCMT) and CIDP might share similar clinical presentations, and sometimes it might be difficult to differentiate them on the basis of the electrodiagnostic findings or cerebrospinal fluid (CSF) albumino-cytological dissociation. This indeed merits early consideration for genetic testing in patients who do not respond to conventional CIDP therapies. Current treatment options for CIDP include intravenous immunoglobulins (IVIG), corticosteroids (CS), and plasmapheresis (PLEX). The need for novel therapies is essential in instances where patients continue to have symptoms despite the standard therapies or due to adverse effects of long-term use of standard therapies such as CS. This paper reviews the challenges in the diagnosis of CIDP in children and the current as well as novel therapies for CIDP.
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LAMA2-related muscular dystrophy is caused by pathogenic variants of the alpha2 subunit of Laminin. This common form of muscular dystrophy is characterized by elevated CK >1000IU/L, dystrophic changes on muscle biopsy, complete or partial absence of merosin staining, and both central and peripheral nervous system involvement. Advancements in genomic testing using NGS and wider application of RNA sequencing has expanded our knowledge of novel non-coding pathogenic variants in LAMA2. RNA sequencing is an increasingly utilized technique to directly analyze the transcriptome, through creation of a complementary DNA (cDNA) from the transcript within a tissue sample. Here we describe a homozygous deep intronic variant that produces a novel splice junction in LAMA2 identified by RNA sequencing analysis in a patient with a clinical phenotype in keeping with LAMA2-related muscular dystrophy. Furthermore, in this case merosin staining was retained suggestive of a functional deficit.
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Íntrons , Laminina , Distrofias Musculares , Análise de Sequência de RNA , Humanos , Laminina/genética , Íntrons/genética , Distrofias Musculares/genética , Distrofias Musculares/patologia , Distrofias Musculares/diagnóstico , Masculino , Fenótipo , Mutação , FemininoRESUMO
Limb girdle muscle dystrophies (LGMDs) are a group of inherited neuromuscular disorders comprising more than 20 genes. There have been increasing efforts to characterize this group with Muscle MRI. However, due to the complexity and similarities, the interpretation of the MRI patterns is usually done by experts in the field. Here, we proposed a step-by-step image interpretation of Muscle MRI in LGDM by evaluating the variability of muscle pattern involvement reported in the literature. A systematic review with an open start date to November 2022 was conducted to describe all LGMDs' muscle MRI patterns. Eighty-eight studies were included in the final review. Data were found to describe muscle MRI patterns for 15 out of 17 LGMDs types. Although the diagnosis of LGMDs is challenging despite the advanced genetic testing and other diagnostic modalities, muscle MRI is shown to help in the diagnosis of LGMDs. To further increase the yield for muscle MRI in the neuromuscular field, larger cohorts of patients need to be conducted.
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Distrofia Muscular do Cíngulo dos Membros , Doenças Neuromusculares , Humanos , Músculo Esquelético/diagnóstico por imagem , Distrofia Muscular do Cíngulo dos Membros/diagnóstico por imagem , Distrofia Muscular do Cíngulo dos Membros/genética , Doenças Neuromusculares/genética , Imageamento por Ressonância Magnética , Testes GenéticosRESUMO
BACKGROUND: Spinal muscular atrophy type 1 (SMA1) is a neuromuscular disorder with a natural history of chronic respiratory failure and death during infancy without ventilation. Recently, disease-modifying therapies such as nusinersen have improved disease trajectory. However, objective data on the trajectory of polysomnography outcomes, the relationship between motor scores and respiratory parameters, respiratory technology dependence and healthcare utilization in children with SMA1 remain to be elucidated. METHODS: This was a retrospective observational study of children with SMA1 receiving nusinersen between October 2016 and February 2021 at two tertiary care hospitals in Canada. Baseline polysomnography data, motor scores, respiratory technology, and unanticipated healthcare utilization were examined. RESULTS: Eleven children (five females, two SMN2 copies each) were included. Median (interquartile range [IQR]) age at diagnosis was 3.6 (2.8-5.0) months and age at diagnostic polysomnogram following nusinersen initiation was 9.4 (5.3-14.0) months. Nusinersen was initiated at a median (IQR) age of 5.4 (3.4-7.6) months and 8/11 children had respiratory symptoms at that time. Diagnostic polysomnography data showed a median (IQR) central apnea-hypopnea index (AHI) of 4.1 (1.8-10.0) and obstructive AHI of 2.2 (0-8.0) events/h. We observed an inverse relationship between motor scores and central apnea-hypopnea indices. All children required ventilatory support at the end of the study period. CONCLUSION: This study showed abnormal polysomnography parameters and need for ventilation despite nusinersen suggesting ongoing need for regular monitoring with polysomnography. Understanding the respiratory disease trajectory of children undergoing treatment with nusinersen will inform decision-making regarding optimal timing of ventilatory support initiation.
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Atrofia Muscular Espinal , Apneia do Sono Tipo Central , Atrofias Musculares Espinais da Infância , Feminino , Criança , Humanos , Lactente , Atrofias Musculares Espinais da Infância/complicações , Atrofias Musculares Espinais da Infância/tratamento farmacológico , Oligonucleotídeos/uso terapêutico , RespiraçãoRESUMO
Phosphoenolpyruvate carboxykinase (PCK) plays a critical role in cytosolic gluconeogenesis, and defects in PCK1 cause a fasting-aggravated metabolic disease with hypoglycemia and lactic acidosis. However, there are two genes encoding PCK, and the role of the mitochondrial resident PCK (encoded by PCK2) is unclear, since gluconeogenesis is cytosolic. We identified three patients in two families with biallelic variants in PCK2. One has compound heterozygous variants (p.Ser23Ter/p.Pro170Leu), and the other two (siblings) have homozygous p.Arg193Ter variation. All three patients have weakness and abnormal gait, an absence of PCK2 protein, and profound reduction in PCK2 activity in fibroblasts, but no obvious metabolic phenotype. Nerve conduction studies showed reduced conduction velocities with temporal dispersion and conduction block compatible with a demyelinating peripheral neuropathy. To validate the association between PCK2 variants and clinical disease, we generated a mouse knockout model of PCK2 deficiency. The animals present abnormal nerve conduction studies and peripheral nerve pathology, corroborating the human phenotype. In total, we conclude that biallelic variants in PCK2 cause a neurogenetic disorder featuring abnormal gait and peripheral neuropathy.