ABSTRACT
A recent study discovered a novel, complex developmental disability syndrome, most likely caused by maternal fentanyl use disorder. This Fetal Fentanyl Syndrome (FFS) is biochemically characterized by elevated 7-dehydrocholesterol (7-DHC) levels in neonates, raising the question if fentanyl inhibition of the dehydrocholesterol reductase 7 (DHCR7) enzyme is causal for the emergence of the pathophysiology and phenotypic features of FFS. To test this hypothesis, we undertook a series of experiments on Neuro2a cells, primary mouse neuronal and astrocytic cultures, and human dermal fibroblasts (HDFs) with DHCR7+/+ and DHCR7+/- genotype. Our results revealed that in vitro exposure to fentanyl disrupted sterol biosynthesis across all four in vitro models. The sterol biosynthesis disruption by fentanyl was complex, and encompassed the majority of post-lanosterol intermediates, including elevated 7-DHC and decreased desmosterol (DES) levels across all investigated models. The overall findings suggested that maternal fentanyl use in the context of an opioid use disorder leads to FFS in the developing fetus through a strong disruption of the whole post-lanosterol pathway that is more complex than a simple DHCR7 inhibition. In follow-up experiments we found that heterozygous DHCR7+/- HDFs were significantly more susceptible to the sterol biosynthesis inhibitory effects of fentanyl than wild-type DHCR7+/+ fibroblasts. These data suggest that DHCR7+/- heterozygosity of mother and/or developing child (and potentially other sterol biosynthesis genes), when combined with maternal fentanyl use disorder, might be a significant contributory factor to the emergence of FFS in the exposed offspring. In a broader context, we believe that evaluation of new and existing medications for their effects on sterol biosynthesis should be an essential consideration during drug safety determinations, especially in pregnancy.
ABSTRACT
BACKGROUND: Neurodevelopmental disorder with dysmorphic facies and distal limb anomalies (NEDDFL) is associated to BPTF gene haploinsufficiency. Epilepsy was not included in the initial descriptions of NEDDFL, but emerging evidence indicates that epileptic seizures occur in some affected individuals. This study aims to investigate the electroclinical epilepsy features in individuals with NEDDFL. METHODS: We enrolled individuals with BPTF-related seizures or interictal epileptiform discharges (IEDs) on electroencephalography (EEG). Demographic, clinical, genetic, raw EEG, and neuroimaging data as well as response to antiseizure medication were assessed. RESULTS: We studied 11 individuals with a null variant in BPTF, including five previously unpublished ones. Median age at last observation was 9 years (range: 4 to 43 years). Eight individuals had epilepsy, one had a single unprovoked seizure, and two showed IEDs only. Key features included (1) early childhood epilepsy onset (median 4 years, range: 10 months to 7 years), (2) well-organized EEG background (all cases) and brief bursts of spikes and slow waves (50% of individuals), and (3) developmental delay preceding seizure onset. Spectrum of epilepsy severity varied from drug-resistant epilepsy (27%) to isolated IEDs without seizures (18%). Levetiracetam was widely used and reduced seizure frequency in 67% of the cases. CONCLUSIONS: Our study provides the first characterization of BPTF-related epilepsy. Early-childhood-onset epilepsy occurs in 19% of subjects, all presenting with a well-organized EEG background associated with generalized interictal epileptiform abnormalities in half of these cases. Drug resistance is rare.
Subject(s)
Electroencephalography , Epilepsy , Phenotype , Humans , Child , Male , Female , Child, Preschool , Epilepsy/physiopathology , Epilepsy/drug therapy , Epilepsy/genetics , Adolescent , Adult , Young AdultABSTRACT
INTRODUCTION: Over 90% of pediatric trauma deaths occur in low- and middle-income countries (LMICs), yet pediatric trauma-focused training remains unstandardized and inaccessible, especially in LMICs. In Brazil, where trauma is the leading cause of death for children over age 1, we piloted the first global adaptation of the Trauma Resuscitation in Kids (TRIK) course and assessed its feasibility. METHODS: A 2-day simulation-based global TRIK course was hosted in Belo Horizonte in October 2022, led by one Brazilian and four Canadian instructors. The enrollment fee was $200 USD, and course registration sold out in 4 d. We administered a knowledge test before and after the course and a postcourse self-evaluation. We recorded each simulation to assess participants' performance, reflected in a team performance score. Groups received numerical scores for these three areas, which were equally weighted to calculate a final performance score. The scores given by the two evaluators were then averaged. As groups performed the specific simulations in varying orders, the simulations were grouped into four time blocks for analysis of performance over time. Statistical analysis utilized a combination of descriptive analysis, Wilcoxon signed-rank tests, Kruskal-Wallis tests, and Wilcoxon rank-sum tests. RESULTS: Twenty-one surgeons (19 pediatric, one trauma, one general) representing four of five regions in Brazil consented to study participation. Women comprised 76% (16/21) of participants. Overall, participants scored higher on the knowledge assessment after the course (68% versus 76%; z = 3.046, P < 0.001). Participants reported improved knowledge for all tested components of trauma management (P < 0.001). The average simulation performance score increased from 66% on day 1% to 73% on day 2, although this increase was not statistically significant. All participants reported they were more confident managing pediatric trauma after the course and would recommend the course to others. CONCLUSIONS: Completion of global TRIK improved surgeons' confidence, knowledge, and clinical decision-making skills in managing pediatric trauma, suggesting a standardized course may improve pediatric trauma care and outcomes in LMICs. We plan to more closely address cost, language, and resource barriers to implementing protocolized trauma training in LMICs with the aim to improve patient outcomes and equity in trauma care globally.
Subject(s)
Developing Countries , Humans , Pilot Projects , Brazil , Child , Wounds and Injuries/therapy , Wounds and Injuries/economics , Female , Traumatology/education , Male , Pediatrics/education , Simulation Training/economics , Clinical Competence/statistics & numerical data , Feasibility Studies , Resuscitation , CurriculumABSTRACT
Biallelic pathogenic variants in ZNF335 are one of the genetic causes of microcephaly, reported only in the past decade. It regulates neural progenitor proliferation and neurogenesis by interacting with a H3K4 methyltransferase complex. Biallelic pathogenic ZNF335 variants predispose to neuronal cell death and aberrant differentiation, thus causing secondary microcephaly. These neurodevelopmental anomalies lead to imaging findings in the cortex, posterior fossa, and basal ganglia. We report an individual of Nepalese ancestry with a novel homozygous ZNF335 variant (c.3591 + 2dup) (p.?) (NM_022095.3) which on further RNA analysis confirmed a splice site variant in intron 23. The patient presented with primary microcephaly with atrophic cerebral hemispheres, oversimplification of gyri, basal ganglia, and corpus callosal atrophy. Literature review on the topic revealed a spectrum of brain abnormalities, which can present either with a primary or secondary microcephaly depending upon the underlying genetic variant.
Subject(s)
Alleles , DNA-Binding Proteins , Microcephaly , Transcription Factors , Humans , Brain/diagnostic imaging , Brain/pathology , Brain/abnormalities , DNA-Binding Proteins/genetics , Genetic Predisposition to Disease , Homozygote , Magnetic Resonance Imaging , Microcephaly/genetics , Microcephaly/pathology , Mutation/genetics , Transcription Factors/geneticsABSTRACT
Pathogenic variants in multiple genes on the X chromosome have been implicated in syndromic and non-syndromic intellectual disability disorders. ZFX on Xp22.11 encodes a transcription factor that has been linked to diverse processes including oncogenesis and development, but germline variants have not been characterized in association with disease. Here, we present clinical and molecular characterization of 18 individuals with germline ZFX variants. Exome or genome sequencing revealed 11 variants in 18 subjects (14 males and 4 females) from 16 unrelated families. Four missense variants were identified in 11 subjects, with seven truncation variants in the remaining individuals. Clinical findings included developmental delay/intellectual disability, behavioral abnormalities, hypotonia, and congenital anomalies. Overlapping and recurrent facial features were identified in all subjects, including thickening and medial broadening of eyebrows, variations in the shape of the face, external eye abnormalities, smooth and/or long philtrum, and ear abnormalities. Hyperparathyroidism was found in four families with missense variants, and enrichment of different tumor types was observed. In molecular studies, DNA-binding domain variants elicited differential expression of a small set of target genes relative to wild-type ZFX in cultured cells, suggesting a gain or loss of transcriptional activity. Additionally, a zebrafish model of ZFX loss displayed an altered behavioral phenotype, providing additional evidence for the functional significance of ZFX. Our clinical and experimental data support that variants in ZFX are associated with an X-linked intellectual disability syndrome characterized by a recurrent facial gestalt, neurocognitive and behavioral abnormalities, and an increased risk for congenital anomalies and hyperparathyroidism.
Subject(s)
Hyperparathyroidism , Intellectual Disability , Neurodevelopmental Disorders , Male , Female , Animals , Humans , Intellectual Disability/pathology , Zebrafish/genetics , Mutation, Missense/genetics , Transcription Factors/genetics , Phenotype , Neurodevelopmental Disorders/geneticsABSTRACT
BACKGROUND: Germline HRAS gain-of-function pathogenic variants cause Costello syndrome (CS). During early childhood, 50% of patients develop multifocal atrial tachycardia, a treatment-resistant tachyarrhythmia of unknown pathogenesis. This study investigated how overactive HRAS activity triggers arrhythmogenesis in atrial-like cardiomyocytes (ACMs) derived from human-induced pluripotent stem cells bearing CS-associated HRAS variants. METHODS: HRAS Gly12 mutations were introduced into a human-induced pluripotent stem cells-ACM reporter line. Human-induced pluripotent stem cells were generated from patients with CS exhibiting tachyarrhythmia. Calcium transients and action potentials were assessed in induced pluripotent stem cell-derived ACMs. Automated patch clamping assessed funny currents. HCN inhibitors targeted pacemaker-like activity in mutant ACMs. Transcriptomic data were analyzed via differential gene expression and gene ontology. Immunoblotting evaluated protein expression associated with calcium handling and pacemaker-nodal expression. RESULTS: ACMs harboring HRAS variants displayed higher beating rates compared with healthy controls. The hyperpolarization activated cyclic nucleotide gated potassium channel inhibitor ivabradine and the Nav1.5 blocker flecainide significantly decreased beating rates in mutant ACMs, whereas voltage-gated calcium channel 1.2 blocker verapamil attenuated their irregularity. Electrophysiological assessment revealed an increased number of pacemaker-like cells with elevated funny current densities among mutant ACMs. Mutant ACMs demonstrated elevated gene expression (ie, ISL1, TBX3, TBX18) related to intracellular calcium homeostasis, heart rate, RAS signaling, and induction of pacemaker-nodal-like transcriptional programming. Immunoblotting confirmed increased protein levels for genes of interest and suppressed MAPK (mitogen-activated protein kinase) activity in mutant ACMs. CONCLUSIONS: CS-associated gain-of-function HRASG12 mutations in induced pluripotent stem cells-derived ACMs trigger transcriptional changes associated with enhanced automaticity and arrhythmic activity consistent with multifocal atrial tachycardia. This is the first human-induced pluripotent stem cell model establishing the mechanistic basis for multifocal atrial tachycardia in CS.
Subject(s)
Induced Pluripotent Stem Cells , Myocytes, Cardiac , Humans , Child, Preschool , Myocytes, Cardiac/metabolism , Calcium/metabolism , Heart Atria/metabolism , Tachycardia , Calcium Channels/metabolism , Induced Pluripotent Stem Cells/metabolism , Action Potentials/physiology , Cell Differentiation , Proto-Oncogene Proteins p21(ras)/genetics , Proto-Oncogene Proteins p21(ras)/metabolismABSTRACT
Germline pathogenic variants in the RAS/mitogen-activated protein kinase (MAPK) signaling pathway are the molecular cause of RASopathies, a group of clinically overlapping genetic syndromes. RASopathies constitute a wide clinical spectrum characterized by distinct facial features, short stature, predisposition to cancer, and variable anomalies in nearly all the major body systems. With increasing global recognition of these conditions, the 8th International RASopathies Symposium spotlighted global perspectives on clinical care and research, including strategies for building international collaborations and developing diverse patient cohorts in anticipation of interventional trials. This biannual meeting, organized by RASopathies Network, was held in a hybrid virtual/in-person format. The agenda featured emerging discoveries and case findings as well as progress in preclinical and therapeutic pipelines. Stakeholders including basic scientists, clinician-scientists, practitioners, industry representatives, patients, and family advocates gathered to discuss cutting edge science, recognize current gaps in knowledge, and hear from people with RASopathies about the experience of daily living. Presentations by RASopathy self-advocates and early-stage investigators were featured throughout the program to encourage a sustainable, diverse, long-term research and advocacy partnership focused on improving health and bringing treatments to people with RASopathies.
Subject(s)
Costello Syndrome , Ectodermal Dysplasia , Heart Defects, Congenital , Neoplasms , Noonan Syndrome , Humans , ras Proteins/genetics , MAP Kinase Signaling System/genetics , Costello Syndrome/genetics , Neoplasms/genetics , Ectodermal Dysplasia/genetics , Noonan Syndrome/genetics , Heart Defects, Congenital/geneticsABSTRACT
PURPOSE: Biallelic variants in TARS2, encoding the mitochondrial threonyl-tRNA-synthetase, have been reported in a small group of individuals displaying a neurodevelopmental phenotype but with limited neuroradiological data and insufficient evidence for causality of the variants. METHODS: Exome or genome sequencing was carried out in 15 families. Clinical and neuroradiological evaluation was performed for all affected individuals, including review of 10 previously reported individuals. The pathogenicity of TARS2 variants was evaluated using in vitro assays and a zebrafish model. RESULTS: We report 18 new individuals harboring biallelic TARS2 variants. Phenotypically, these individuals show developmental delay/intellectual disability, regression, cerebellar and cerebral atrophy, basal ganglia signal alterations, hypotonia, cerebellar signs, and increased blood lactate. In vitro studies showed that variants within the TARS2301-381 region had decreased binding to Rag GTPases, likely impairing mTORC1 activity. The zebrafish model recapitulated key features of the human phenotype and unraveled dysregulation of downstream targets of mTORC1 signaling. Functional testing of the variants confirmed the pathogenicity in a zebrafish model. CONCLUSION: We define the clinico-radiological spectrum of TARS2-related mitochondrial disease, unveil the likely involvement of the mTORC1 signaling pathway as a distinct molecular mechanism, and establish a TARS2 zebrafish model as an important tool to study variant pathogenicity.
Subject(s)
RNA, Transfer , Zebrafish , Animals , Humans , Mutation , Zebrafish/genetics , Mechanistic Target of Rapamycin Complex 1 , Ligases , PhenotypeABSTRACT
Cornelia de Lange Syndrome (CdLS) is a rare, dominantly inherited multisystem developmental disorder characterized by highly variable manifestations of growth and developmental delays, upper limb involvement, hypertrichosis, cardiac, gastrointestinal, craniofacial, and other systemic features. Pathogenic variants in genes encoding cohesin complex structural subunits and regulatory proteins (NIPBL, SMC1A, SMC3, HDAC8, and RAD21) are the major pathogenic contributors to CdLS. Heterozygous or hemizygous variants in the genes encoding these five proteins have been found to be contributory to CdLS, with variants in NIPBL accounting for the majority (>60%) of cases, and the only gene identified to date that results in the severe or classic form of CdLS when mutated. Pathogenic variants in cohesin genes other than NIPBL tend to result in a less severe phenotype. Causative variants in additional genes, such as ANKRD11, EP300, AFF4, TAF1, and BRD4, can cause a CdLS-like phenotype. The common role that these genes, and others, play as critical regulators of developmental transcriptional control has led to the conditions they cause being referred to as disorders of transcriptional regulation (or "DTRs"). Here, we report the results of a comprehensive molecular analysis in a cohort of 716 probands with typical and atypical CdLS in order to delineate the genetic contribution of causative variants in cohesin complex genes as well as novel candidate genes, genotype-phenotype correlations, and the utility of genome sequencing in understanding the mutational landscape in this population.
Subject(s)
De Lange Syndrome , Nuclear Proteins , Humans , Nuclear Proteins/genetics , De Lange Syndrome/diagnosis , De Lange Syndrome/genetics , De Lange Syndrome/pathology , Transcription Factors/genetics , Cell Cycle Proteins/genetics , Phenotype , Mutation , Genomics , Genetic Association Studies , Transcriptional Elongation Factors/genetics , Histone Deacetylases/genetics , Repressor Proteins/geneticsABSTRACT
Pour traiter l'acidocétose diabétique pédiatrique, il faut porter une attention particulière aux liquides et aux électrolytes pour limiter le risque de complications, telles qu'une lésion cérébrale, associée à une morbidité et une mortalité élevées. L'incidence d'Ådème cérébral en cas d'acidocétose diabétique n'a pas diminué malgré les protocoles visant la limitation des liquides qui s'appuient sur la restriction de la réanimation liquidienne initiale. Selon de nouvelles données probantes, l'administration précoce de liquides isotoniques n'entraîne pas de risque supplémentaire et peut améliorer les résultats cliniques chez certains patients. Les protocoles et les directives cliniques sont adaptés et axés particulièrement sur la surveillance et le remplacement initiaux et continus des liquides et des électrolytes. Il est maintenant recommandé de commencer par une réanimation à l'aide de liquides isotoniques chez tous les patients dans les 20 à 30 minutes suivant leur arrivée à l'hôpital, suivie par la réplétion du déficit volumique sur une période de 36 heures, en association avec une perfusion d'insuline et des suppléments d'électrolytes, ainsi qu'avec la surveillance et la prise en charge attentives d'une éventuelle lésion cérébrale.
ABSTRACT
Treatment of paediatric diabetic ketoacidosis (DKA) includes careful attention to fluids and electrolytes to minimize the risk of complications such as cerebral injury (CI), which is associated with high morbidity and mortality. The incidence of cerebral edema in paediatric DKA has not decreased despite the use of fluid-limiting protocols based on restricting early fluid resuscitation. New evidence suggests that early isotonic fluid therapy does not confer additional risk and may improve outcomes in some patients. Protocols and clinical practice guidelines are being adjusted, with a particular focus on recommendations for initial and ongoing fluids and electrolyte monitoring and replacement. Initial isotonic fluid resuscitation is now recommended for all patients in the first 20 to 30 minutes after presentation, followed by repletion of volume deficit over 36 hours in association with an insulin infusion, electrolyte supplementation, and careful monitoring for and management of potential CI.
ABSTRACT
WWOX biallelic loss-of-function pathogenic single nucleotide variants (SNVs) and copy number variants (CNVs) including exonic deletions and duplications cause WWOX-related epileptic encephalopathy (WOREE) syndrome. This disorder is characterized by refractory epilepsy, axial hypotonia, peripheral hypertonia, progressive microcephaly, and premature death. Here we report five patients with WWOX biallelic predicted null variants identified by exome sequencing (ES), genome sequencing (GS), and/or chromosomal microarray analysis (CMA). SNVs and intragenic deletions of one or more exons were commonly reported in WOREE syndrome patients which made the genetic diagnosis challenging and required a combination of different diagnostic technologies. These patients presented with severe, developmental and epileptic encephalopathy (DEE), and other cardinal features consistent with WOREE syndrome. This report expands the clinical phenotype associated with this condition, including failure to thrive in most patients and epilepsy that responded to a ketogenic diet in three patients. Dysmorphic features and abnormal prenatal findings were not commonly observed. Additionally, recurrent pancreatitis and sensorineural hearing loss each were observed in single patients. In summary, these phenotypic features broaden the clinical spectrum of WOREE syndrome.
Subject(s)
Brain Diseases , Epilepsy, Generalized , Epilepsy , Epileptic Syndromes , Female , Pregnancy , Humans , Epilepsy/diagnosis , Epilepsy/genetics , Epileptic Syndromes/genetics , Brain Diseases/genetics , Epilepsy, Generalized/genetics , Exons , WW Domain-Containing Oxidoreductase/genetics , Tumor Suppressor Proteins/geneticsABSTRACT
Central nervous system (CNS) anomalies are common in individuals with RASopathies. While certain findings, including relative or absolute macrocephaly, are typical for most RASopathies, other findings are more common in certain conditions, with rare low-grade gliomas in Noonan syndrome (NS); Chiari 1 malformation and tethered cord in Costello syndrome (CS); and variable structural anomalies including heterotopia and hydrocephalus in cardio-facio-cutaneous syndrome (CFC). We performed a literature review and present aggregate data on the common and uncommon CNS manifestations in individuals with RASopathies. A gene-based approach to defining risk for specific abnormalities may be considered. However, limited information on the CNS findings of rare RASopathies, such as autosomal recessive LZTR1-related NS or PPP1CB-related NS with loose anagen hair (NSLH), is currently available. Thus, consideration of the RASopathies as a group of distinct syndromic conditions with shared underlying causes and overlapping clinical presentations remains relevant, and individuals with a RASopathy are at risk for many findings seen in these conditions.
Subject(s)
Heart Defects, Congenital , Noonan Syndrome , Humans , Noonan Syndrome/genetics , Failure to Thrive , Facies , Central Nervous System , Mutation , Transcription FactorsABSTRACT
RASopathies are a group of genetic disorders that are caused by genes that affect the canonical Ras/mitogen-activated protein kinase (MAPK) signaling pathway. Despite tremendous progress in understanding the molecular consequences of these genetic anomalies, little movement has been made in translating these findings to the clinic. This year, the seventh International RASopathies Symposium focused on expanding the research knowledge that we have gained over the years to enhance new discoveries in the field, ones that we hope can lead to effective therapeutic treatments. Indeed, for the first time, research efforts are finally being translated to the clinic, with compassionate use of Ras/MAPK pathway inhibitors for the treatment of RASopathies. This biannual meeting, organized by the RASopathies Network, brought together basic scientists, clinicians, clinician scientists, patients, advocates, and their families, as well as representatives from pharmaceutical companies and the National Institutes of Health. A history of RASopathy gene discovery, identification of new disease genes, and the latest research, both at the bench and in the clinic, were discussed.
Subject(s)
Costello Syndrome , Noonan Syndrome , Costello Syndrome/genetics , Humans , Mitogen-Activated Protein Kinases/metabolism , Noonan Syndrome/genetics , Signal Transduction , ras Proteins/genetics , ras Proteins/metabolismABSTRACT
Many monogenic disorders cause a characteristic facial morphology. Artificial intelligence can support physicians in recognizing these patterns by associating facial phenotypes with the underlying syndrome through training on thousands of patient photographs. However, this 'supervised' approach means that diagnoses are only possible if the disorder was part of the training set. To improve recognition of ultra-rare disorders, we developed GestaltMatcher, an encoder for portraits that is based on a deep convolutional neural network. Photographs of 17,560 patients with 1,115 rare disorders were used to define a Clinical Face Phenotype Space, in which distances between cases define syndromic similarity. Here we show that patients can be matched to others with the same molecular diagnosis even when the disorder was not included in the training set. Together with mutation data, GestaltMatcher could not only accelerate the clinical diagnosis of patients with ultra-rare disorders and facial dysmorphism but also enable the delineation of new phenotypes.
Subject(s)
Artificial Intelligence , Rare Diseases , Face , Humans , Neural Networks, Computer , Phenotype , Rare Diseases/geneticsABSTRACT
Costello syndrome (CS) is an autosomal dominant disorder caused by pathogenic variants in HRAS. Craniosynostosis is a known feature of other RASopathies (Noonan and cardiofaciocutaneous syndromes) but not CS. We describe four individuals with CS and craniosynostosis and present a summary of all previously reported individuals with craniosynostosis and RASopathy.
Subject(s)
Costello Syndrome , Craniosynostoses , Ectodermal Dysplasia , Noonan Syndrome , Costello Syndrome/diagnosis , Costello Syndrome/genetics , Craniosynostoses/diagnosis , Craniosynostoses/genetics , Facies , Failure to Thrive , HumansABSTRACT
Subcellular membrane systems are highly enriched in dolichol, whose role in organelle homeostasis and endosomal-lysosomal pathway remains largely unclear besides being involved in protein glycosylation. DHDDS encodes for the catalytic subunit (DHDDS) of the enzyme cis-prenyltransferase (cis-PTase), involved in dolichol biosynthesis and dolichol-dependent protein glycosylation in the endoplasmic reticulum. An autosomal recessive form of retinitis pigmentosa (retinitis pigmentosa 59) has been associated with a recurrent DHDDS variant. Moreover, two recurring de novo substitutions were detected in a few cases presenting with neurodevelopmental disorder, epilepsy and movement disorder. We evaluated a large cohort of patients (n = 25) with de novo pathogenic variants in DHDDS and provided the first systematic description of the clinical features and long-term outcome of this new neurodevelopmental and neurodegenerative disorder. The functional impact of the identified variants was explored by yeast complementation system and enzymatic assay. Patients presented during infancy or childhood with a variable association of neurodevelopmental disorder, generalized epilepsy, action myoclonus/cortical tremor and ataxia. Later in the disease course, they experienced a slow neurological decline with the emergence of hyperkinetic and/or hypokinetic movement disorder, cognitive deterioration and psychiatric disturbances. Storage of lipidic material and altered lysosomes were detected in myelinated fibres and fibroblasts, suggesting a dysfunction of the lysosomal enzymatic scavenger machinery. Serum glycoprotein hypoglycosylation was not detected and, in contrast to retinitis pigmentosa and other congenital disorders of glycosylation involving dolichol metabolism, the urinary dolichol D18/D19 ratio was normal. Mapping the disease-causing variants into the protein structure revealed that most of them clustered around the active site of the DHDDS subunit. Functional studies using yeast complementation assay and in vitro activity measurements confirmed that these changes affected the catalytic activity of the cis-PTase and showed growth defect in yeast complementation system as compared with the wild-type enzyme and retinitis pigmentosa-associated protein. In conclusion, we characterized a distinctive neurodegenerative disorder due to de novo DHDDS variants, which clinically belongs to the spectrum of genetic progressive encephalopathies with myoclonus. Clinical and biochemical data from this cohort depicted a condition at the intersection of congenital disorders of glycosylation and inherited storage diseases with several features akin to of progressive myoclonus epilepsy such as neuronal ceroid lipofuscinosis and other lysosomal disorders.