ABSTRACT
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.
Subject(s)
Exome , Rare Diseases , Humans , Prospective Studies , Exome Sequencing , Rare Diseases/diagnosis , Rare Diseases/genetics , Genetic Testing/methods , OntarioABSTRACT
PURPOSE: KLHL20 is part of a CUL3-RING E3 ubiquitin ligase involved in protein ubiquitination. KLHL20 functions as the substrate adaptor that recognizes substrates and mediates the transfer of ubiquitin to the substrates. Although KLHL20 regulates neurite outgrowth and synaptic development in animal models, a role in human neurodevelopment has not yet been described. We report on a neurodevelopmental disorder caused by de novo missense variants in KLHL20. METHODS: Patients were ascertained by the investigators through Matchmaker Exchange. Phenotyping of patients with de novo missense variants in KLHL20 was performed. RESULTS: We studied 14 patients with de novo missense variants in KLHL20, delineating a genetic syndrome with patients having mild to severe intellectual disability, febrile seizures or epilepsy, autism spectrum disorder, hyperactivity, and subtle dysmorphic facial features. We observed a recurrent de novo missense variant in 11 patients (NM_014458.4:c.1069G>A p.[Gly357Arg]). The recurrent missense and the 3 other missense variants all clustered in the Kelch-type ß-propeller domain of the KLHL20 protein, which shapes the substrate binding surface. CONCLUSION: Our findings implicate KLHL20 in a neurodevelopmental disorder characterized by intellectual disability, febrile seizures or epilepsy, autism spectrum disorder, and hyperactivity.
Subject(s)
Autism Spectrum Disorder , Epilepsy , Intellectual Disability , Seizures, Febrile , Child , Humans , Adaptor Proteins, Signal Transducing/genetics , Autism Spectrum Disorder/genetics , Developmental Disabilities , Epilepsy/genetics , Intellectual Disability/genetics , Mutation, Missense/genetics , Ubiquitin-Protein Ligases/geneticsABSTRACT
BACKGROUND: Glucose Transporter-1 (GLUT1) Deficiency Syndrome (GLUT1DS) is caused by defective transport of glucose across the blood-brain barrier into brain cells resulting in hypoglycorrhachia due to the heterozygous pathogenic variants in SLC2A1. We report on the phenotypic spectrum of patients with pediatric GLUT1DS as well as their diagnostic methods from a single center in Canada. METHODS: We reviewed patient charts for clinical features, biochemical and molecular genetic investigations, neuroimaging, treatment modalities, and outcomes of patients with GLUT1DS at our institution. RESULTS: There were 13 patients. The most common initial symptom was seizures, with the most common seizure type being absence seizures (85%). Seventy-seven percent of the patients had movement disorders, and dystonia and ataxia were the most common movement disorders. Fifty-four percent of the patients did not have a history of developmental delay during their initial presentation, whereas all patients had developmental delay, intellectual disability, or cognitive dysfunction during their follow-up. All patients had a pathogenic or likely pathogenic variant in SLC2A1 and missense variants were the most common variant type. CONCLUSION: We present 13 patients with GLUT1DS in the pediatric patient population. Atypical clinical features such as hemiplegia and hemiplegic migraine were present in an infant; there was a high prevalence of absence seizures and movement disorders in our patient population. We report an increased number of patients with GLUT1DS since the introduction of next-generation sequencing in the clinical settings. We believe that GLUT1DS should be included in the differential diagnosis of seizures, movement disorders, and hemiplegic migraine.
Subject(s)
Carbohydrate Metabolism, Inborn Errors , Diet, Ketogenic , Glucose Transporter Type 1/metabolism , Carbohydrate Metabolism, Inborn Errors/diagnosis , Carbohydrate Metabolism, Inborn Errors/genetics , Child , Diet, Ketogenic/methods , Glucose Transport Proteins, Facilitative , Glucose Transporter Type 1/genetics , Humans , Infant , Monosaccharide Transport Proteins/genetics , Seizures/geneticsABSTRACT
Glutamatergic neurotransmission governs excitatory signaling in the mammalian brain, and abnormalities of glutamate signaling have been shown to contribute to both epilepsy and hyperkinetic movement disorders. The etiology of many severe childhood movement disorders and epilepsies remains uncharacterized. We describe a neurological disorder with epilepsy and prominent choreoathetosis caused by biallelic pathogenic variants in FRRS1L, which encodes an AMPA receptor outer-core protein. Loss of FRRS1L function attenuates AMPA-mediated currents, implicating chronic abnormalities of glutamatergic neurotransmission in this monogenic neurological disease of childhood.
Subject(s)
Brain Diseases/genetics , Epilepsy/genetics , Hyperkinesis/genetics , Membrane Proteins/genetics , Mutation/genetics , Nerve Tissue Proteins/genetics , Synaptic Transmission/physiology , Electrophysiology , Female , Humans , Infant , Male , Pedigree , alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/metabolismABSTRACT
PurposeGenetic testing is an integral diagnostic component of pediatric medicine. Standard of care is often a time-consuming stepwise approach involving chromosomal microarray analysis and targeted gene sequencing panels, which can be costly and inconclusive. Whole-genome sequencing (WGS) provides a comprehensive testing platform that has the potential to streamline genetic assessments, but there are limited comparative data to guide its clinical use.MethodsWe prospectively recruited 103 patients from pediatric non-genetic subspecialty clinics, each with a clinical phenotype suggestive of an underlying genetic disorder, and compared the diagnostic yield and coverage of WGS with those of conventional genetic testing.ResultsWGS identified diagnostic variants in 41% of individuals, representing a significant increase over conventional testing results (24%; P = 0.01). Genes clinically sequenced in the cohort (n = 1,226) were well covered by WGS, with a median exonic coverage of 40 × ±8 × (mean ±SD). All the molecular diagnoses made by conventional methods were captured by WGS. The 18 new diagnoses made with WGS included structural and non-exonic sequence variants not detectable with whole-exome sequencing, and confirmed recent disease associations with the genes PIGG, RNU4ATAC, TRIO, and UNC13A.ConclusionWGS as a primary clinical test provided a higher diagnostic yield than conventional genetic testing in a clinically heterogeneous cohort.
Subject(s)
Genetic Association Studies , Genetic Diseases, Inborn/diagnosis , Genetic Diseases, Inborn/genetics , Genetic Predisposition to Disease , Genetic Testing , Sequence Analysis, DNA , Whole Genome Sequencing , Computational Biology/methods , DNA Copy Number Variations , Exome , Female , Genetic Association Studies/methods , Genetic Association Studies/standards , Genetic Testing/methods , Genetic Testing/standards , Genetic Variation , Humans , Male , Molecular Sequence Annotation , Phenotype , Sequence Analysis, DNA/methods , Sequence Analysis, DNA/standards , Exome Sequencing/methods , Exome Sequencing/standards , Whole Genome Sequencing/methods , Whole Genome Sequencing/standardsABSTRACT
Biallelic likely pathogenic variants in SLC52A2 and SLC52A3 cause riboflavin transporter deficiency. It is characterized by muscle weakness, ataxia, progressive ponto-bulbar palsy, amyotrophy, and sensorineural hearing loss. Oral riboflavin halts disease progression and may reverse symptoms. We report two new patients whose clinical and biochemical features were mimicking mitochondrial myopathy. Patient 1 is an 8-year-old male with global developmental delay, axial and appendicular hypotonia, ataxia, and sensorineural hearing loss. His muscle biopsy showed complex II deficiency and ragged red fibers consistent with mitochondrial myopathy. Whole exome sequencing revealed a homozygous likely pathogenic variant in SLC52A2 (c.917G>A; p.Gly306Glu). Patient 2 is a 14-month-old boy with global developmental delay, respiratory insufficiency requiring ventilator support within the first year of life. His muscle biopsy revealed combined complex II + III deficiency and ragged red fibers consistent with mitochondrial myopathy. Whole exome sequencing identified a homozygous likely pathogenic variant in SCL52A3 (c.1223G>A; p.Gly408Asp). We report two new patients with riboflavin transporter deficiency, caused by mutations in two different riboflavin transporter genes. Both patients presented with complex II deficiency. This treatable neurometabolic disorder can mimic mitochondrial myopathy. In patients with complex II deficiency, riboflavin transporter deficiency should be included in the differential diagnosis to allow early treatment and improve neurodevelopmental outcome.
Subject(s)
Electron Transport Complex III/deficiency , Electron Transport Complex II/deficiency , Membrane Transport Proteins/genetics , Mitochondrial Myopathies/genetics , Receptors, G-Protein-Coupled/genetics , Biopsy , Child , Developmental Disabilities/genetics , Developmental Disabilities/physiopathology , Disease Progression , Electron Transport Complex II/genetics , Electron Transport Complex III/genetics , Hearing Loss, Sensorineural/genetics , Hearing Loss, Sensorineural/physiopathology , Humans , Infant , Male , Metabolism, Inborn Errors , Mitochondrial Diseases , Mitochondrial Myopathies/physiopathology , Riboflavin/genetics , Riboflavin/metabolism , Riboflavin Deficiency/genetics , Riboflavin Deficiency/physiopathologyABSTRACT
We report the outcome of 12 patients with inherited neurotransmitter disorders of monoamine, tetrahydrobiopterin and γ amino butyric acid metabolisms from a single Inherited Neurotransmitter Disorder Clinic including tyrosine hydroxylase (n=2), aromatic l-amino acid decarboxylase (n=1), 6-pyruvoyltetrahydropterin synthase, dihydropteridine reductase and succinic semialdehyde dehydrogenase deficiencies. Six patients (with 6-pyruvoyltetrahydropterin synthase, dihydropteridine reductase and tyrosine hydroxylase deficiencies) had normal neurodevelopmental outcome on treatment. Tetrahydrobiopterin loading test in newborns with positive newborn screening for phenylketonuria will identify patients with 6-pyruvoyltetrahydropterin synthase and dihydropteridine reductase deficiencies resulting in abnormal neurotransmitter synthesis in the central nervous system in the neonatal period to initiate disease-specific treatment to improve neurodevelopmental outcome.
Subject(s)
Amino Acid Metabolism, Inborn Errors/genetics , Amino Acid Metabolism, Inborn Errors/metabolism , Amino Acid Metabolism, Inborn Errors/therapy , Neurotransmitter Agents/metabolism , Treatment Outcome , Adolescent , Amino Acid Metabolism, Inborn Errors/complications , Child , Child, Preschool , Cognition Disorders/etiology , Female , Humans , Infant , Male , Neuropsychological TestsABSTRACT
BACKGROUND: Congenital disorders of glycosylation (CDG) are inborn defects of glycan metabolism. They are multisystem disorders. Analysis of transferrin isoforms is applied as a screening test for CDG type I (CDG-I) and type II (CDG-II). We performed a retrospective cohort study to determine spectrum of phenotype and genotype and prevalence of the different subtypes of CDG-I and CDG-II. MATERIAL AND METHODS: All patients with CDG-I and CDG-II evaluated in our institution's Metabolic Genetics Clinics were included. Electronic and paper patient charts were reviewed. We set-up a high performance liquid chromatography transferrin isoelectric focusing (TIEF) method to measure transferrin isoforms in our Institution. We reviewed the literature for the rare CDG-I and CDG-II subtypes seen in our Institution. RESULTS: Fifteen patients were included: 9 with PMM2-CDG and 6 with non-PMM2-CDG (one ALG3-CDG, one ALG9-CDG, two ALG11-CDG, one MPDU1-CDG and one ATP6V0A2-CDG). All patients with PMM2-CDG and 5 patients with non-PMM2-CDG showed abnormal TIEF suggestive of CDG-I or CDG-II pattern. In all patients, molecular diagnosis was confirmed either by single gene testing, targeted next generation sequencing for CDG genes, or by whole exome sequencing. CONCLUSION: We report 15 new patients with CDG-I and CDG-II. Whole exome sequencing will likely identify more patients with normal TIEF and expand the phenotypic spectrum of CDG-I and CDG-II.
Subject(s)
Congenital Disorders of Glycosylation/classification , Congenital Disorders of Glycosylation/diagnosis , Gene Regulatory Networks , High-Throughput Nucleotide Sequencing/methods , Sequence Analysis, DNA/methods , Transferrin/metabolism , Adolescent , Child , Child, Preschool , Chromatography, High Pressure Liquid , Congenital Disorders of Glycosylation/genetics , Congenital Disorders of Glycosylation/metabolism , Exome , Female , Genetic Predisposition to Disease , Genotype , Humans , Infant , Male , Phenotype , Protein Isoforms/metabolism , Retrospective StudiesABSTRACT
We report treatment outcome of eleven patients with pyridoxine-dependent epilepsy caused by pathogenic variants in ALDH7A1 (PDE-ALDH7A1). We developed a clinical severity score to compare phenotype with biochemical features, genotype and delays in the initiation of pyridoxine. Clinical severity score included 1) global developmental delay/ intellectual disability; 2) age of seizure onset prior to pyridoxine; 3) current seizures on treatment. Phenotype scored 1-3 = mild; 4-6 = moderate; and 7-9 = severe. Five patients had mild, four patients had moderate, and two patients had severe phenotype. Phenotype ranged from mild to severe in eight patients (no lysine-restricted diet in the infantile period) with more than 10-fold elevated urine or plasma α-AASA levels. Phenotype ranged from mild to moderate in patients with homozygous truncating variants and from moderate to severe in patients with homozygous missense variants. There was no correlation between severity of the phenotype and the degree of α-AASA elevation in urine or genotype. All patients were on pyridoxine, nine patients were on arginine and five patients were on the lysine-restricted diet. 73% of the patients became seizure free on pyridoxine. 25% of the patients had a mild phenotype on pyridoxine monotherapy. Whereas, 100% of the patients, on the lysine-restricted diet initiated within their first 7 months of life, had a mild phenotype. Early initiation of lysine-restricted diet and/or arginine therapy likely improved neurodevelopmental outcome in young patients with PDE-ALDH7A1.
Subject(s)
Epilepsy/drug therapy , Epilepsy/genetics , Pyridoxine/therapeutic use , Vitamins/therapeutic use , 2-Aminoadipic Acid/analogs & derivatives , 2-Aminoadipic Acid/blood , 2-Aminoadipic Acid/urine , Adolescent , Aldehyde Dehydrogenase/genetics , Arginine/therapeutic use , Child , Child, Preschool , Cohort Studies , Female , Genotype , Humans , Infant , Lysine , Male , Mutation, Missense , Phenotype , Pyridoxine/administration & dosage , Retrospective Studies , Seizures/drug therapy , Seizures/physiopathology , Treatment Outcome , Vitamins/administration & dosageABSTRACT
OBJECTIVE: Epilepsy is a common neurologic disorder of childhood. To determine the genetic diagnostic yield in epileptic encephalopathy, we performed a retrospective cohort study in a single epilepsy genetics clinic. METHODS: We included all patients with intractable epilepsy, global developmental delay, and cognitive dysfunction seen between January 2012 and June 2014 in the Epilepsy Genetics Clinic. Electronic patient charts were reviewed for clinical features, neuroimaging, biochemical investigations, and molecular genetic investigations including targeted next-generation sequencing of epileptic encephalopathy genes. RESULTS: Genetic causes were identified in 28% of the 110 patients: 7% had inherited metabolic disorders including pyridoxine dependent epilepsy caused by ALDH7A1 mutation, Menkes disease, pyridox(am)ine-5-phosphate oxidase deficiency, cobalamin G deficiency, methylenetetrahydrofolate reductase deficiency, glucose transporter 1 deficiency, glycine encephalopathy, and pyruvate dehydrogenase complex deficiency; 21% had other genetic causes including genetic syndromes, pathogenic copy number variants on array comparative genomic hybridization, and epileptic encephalopathy related to mutations in the SCN1A, SCN2A, SCN8A, KCNQ2, STXBP1, PCDH19, and SLC9A6 genes. Forty-five percent of patients obtained a genetic diagnosis by targeted next-generation sequencing epileptic encephalopathy panels. It is notable that 4.5% of patients had a treatable inherited metabolic disease. SIGNIFICANCE: To the best of our knowledge, this is the first study to combine inherited metabolic disorders and other genetic causes of epileptic encephalopathy. Targeted next-generation sequencing panels increased the genetic diagnostic yield from <10% to >25% in patients with epileptic encephalopathy.
Subject(s)
Genetic Predisposition to Disease , Mutation/genetics , Spasms, Infantile/diagnosis , Spasms, Infantile/genetics , Adolescent , Cadherins , Child , Child, Preschool , Cognition Disorders/complications , Cognition Disorders/genetics , Cohort Studies , Developmental Disabilities/complications , Developmental Disabilities/genetics , Female , Humans , Infant , KCNQ2 Potassium Channel , Male , Munc18 Proteins , NAV1.2 Voltage-Gated Sodium Channel , Protocadherins , Sodium-Hydrogen Exchangers , Spasms, Infantile/complicationsABSTRACT
INTRODUCTION: Childhood epilepsy is one of the most common neurological problems. The transferrin isoelectric focusing (TIEF) test is a screening test for congenital disorders of glycosylation (CDG). We identified abnormal TIEF test in children with epilepsy in our epilepsy genetics clinic. To determine if an abnormal TIEF test is associated with anti-epileptic medications or abnormal liver functions, we performed a retrospective cohort study. METHODS: This study was performed between January 2012 and March 2020. Electronic patient charts were reviewed. Standard non-parametric statistical tests were applied using R statistical software. Fischer's exact test was used for comparisons. RESULTS: There were 206 patients. The TIEF test was abnormal in 11% (23 out of 206) of the patients. Nine patients were diagnosed with CDG: PMM2-CDG (n = 5), ALG3-CDG (n = 1), ALG11-CDG (n = 2), SLC35A2-CDG (n = 1). We report 51 different genetic diseases in 84 patients. Two groups, (1) abnormal TIEF test; (2) normal TIEF test, showed statistically significant differences for abnormal liver functions and for valproic acid treatment. CONCLUSION: The TIEF test guided CDG diagnosis in 2.9% of the patients. Due to the high prevalence of CDG (4.4%) in childhood epilepsy, the TIEF test might be included into the diagnostic investigations to allow earlier and cost-effective diagnosis.
Subject(s)
Anticonvulsants/therapeutic use , Congenital Disorders of Glycosylation/epidemiology , Epilepsy/drug therapy , Epilepsy/genetics , Isoelectric Focusing/methods , Transferrin/metabolism , Adolescent , Anticonvulsants/adverse effects , Child , Child, Preschool , Congenital Disorders of Glycosylation/genetics , Female , Humans , Liver Function Tests , Male , Prevalence , Retrospective StudiesABSTRACT
BACKGROUND: Cerebral creatine deficiency disorders (CCDD) are inherited metabolic disorders of creatine synthesis and transport. Urine creatine metabolite panel is helpful to identify these disorders. METHODS: We reviewed electronic patient charts for all patients that underwent urine creatine metabolite panel testing in the metabolic laboratory at our institution. RESULTS: There were 498 tests conducted on 413 patients. Clinical, molecular genetics and neuroimaging features were available in 318 patients. Two new patients were diagnosed with creatine transporter deficiency: one female and one male, both had markedly elevated urine creatine. Urine creatine metabolite panel was also used as a monitoring test in our metabolic laboratory. Diagnostic yield of urine creatine metabolite panel was 0.67% (2/297). There were six known patients with creatine transporter deficiency. The prevalence of creatine transporter deficiency was 2.64% in our study in patients with neurodevelopmental disorders who underwent screening or monitoring of CCDS at our institution. CONCLUSION: Even though the diagnostic yield of urine creatine metabolite panel is low, it can successfully detect CCDD patients, despite many neurodevelopmental disorders are not a result of CCDD. To the best of our knowledge, this study is the first Canadian study to report diagnostic yield of urine creatine metabolite panel for CCDD from a single center.
Subject(s)
Brain Diseases, Metabolic, Inborn , Movement Disorders , Neurodevelopmental Disorders , Brain Diseases, Metabolic, Inborn/diagnosis , Brain Diseases, Metabolic, Inborn/genetics , Canada , Creatine , Female , Guanidinoacetate N-Methyltransferase , Humans , Male , Neurodevelopmental Disorders/diagnosis , Neurodevelopmental Disorders/geneticsABSTRACT
Genetic diagnosis of childhood epilepsy is crucial to provide disease-specific treatments. This report describes the genetic landscape of childhood epilepsy revealed by targeted next-generation sequencing panels for epilepsy (TNGSP-E) and whole exome sequencing (WES). In this retrospective cohort study, TNGSP-E and/or WES were applied to identify underlying genetic diagnoses in children seen in a single Pediatric Epilepsy Genetics Clinic. We reviewed electronic patient charts for phenotypes and biochemical, genetic, and neuroimaging investigations. Forty-four different genetic diagnoses were confirmed in 71 of 197 patients (36%; 95% CI 29.3%-43.2%). The diagnostic yield of WES (37%) was 1.9-fold greater than the diagnostic yield of TNGSP-E (19.0%; P=.0018). The number of genes included in TNGSP-E was not correlated with whether or not the test resulted in a diagnosis (Pearson's R=-0.02, P=.8). Inherited metabolic disorders accounted for 13% of the genetic diagnoses, despite abnormal metabolic investigations being an exclusion criteria. There was a direct treatment implication in 6% of patients with inherited metabolic disorders including pyridoxine dependent epilepsy, glucose transporter 1 deficiency and neuronal ceroid lipofuscinosis type 2. Additionally, there might be some treatment implications in 30% of patients with genetic diagnoses including SCN1A, SCN2A, SCN8A, and KCNQ2 associated epilepsies by application of effective anti-epileptic drugs or the ketogenic diet therapy. The high diagnostic yield of clinical molecular genetic investigations and their disease-specific treatment implications highlight the importance of genetic diagnosis in childhood epilepsy. We recommend a stepwise diagnostic algorithm including metabolic investigations for treatable disorders, chromosomal microarray analysis, TNGSP-E, and WES.
Subject(s)
Epilepsy/drug therapy , Epilepsy/genetics , Brain Diseases, Metabolic/genetics , Child , Child, Preschool , Cohort Studies , Female , High-Throughput Nucleotide Sequencing , Humans , Infant , Male , Mutation/genetics , Phenotype , Retrospective Studies , Exome SequencingABSTRACT
Hyperphenylalaninemia, movement disorder, and intellectual disability due to variants in DNAJC12 is a recently reported inherited neurotransmitter disorder. We report two new patients with this new genetic disorder. Patient 1 is a 6-year-11-month-old boy with mild hyperphenylalaninemia and global developmental delay (GDD). Seventeen-year-old male sibling of patient 1 had GDD from the first year of life. He had mild hyperphenylalaninemia at 11.5 years of age following his younger brother's diagnosis. He had low levels of homovanillic acid and 5-hydroxyindolacetic acid in the cerebrospinal fluid. Whole-exome sequencing (WES) was normal in 2016. After the first description of DNAJC12-associated hyperphenylalaninemia, dystonia, and intellectual disability in 2017, WES re-analysis identified a homozygous c.58_59delGG (p.(Gly20Metfs*2)) variant in DNAJC12. His younger brother was homozygous for the same variant, confirming the diagnosis of DNAJC12-associated hyperphenylalaninemia, movement disorder, and intellectual disability. Mild hyperphenylalaninemia and GDD should warrant targeted DNAJC12 genetic testing for the early diagnosis of DNAJC12-associated hyperphenylalaninemia, movement disorder, and intellectual disability.
Subject(s)
Developmental Disabilities/genetics , Movement Disorders/genetics , Phenylketonurias/genetics , Repressor Proteins/genetics , Adolescent , Child , Developmental Disabilities/pathology , Humans , Male , Movement Disorders/pathology , Mutation , Phenylketonurias/pathology , SiblingsABSTRACT
OBJECTIVE: To identify underlying genetic causes in patients with pediatric movement disorders by genetic investigations. METHODS: All patients with a movement disorder seen in a single Pediatric Genetic Movement Disorder Clinic were included in this retrospective cohort study. We reviewed electronic patient charts for clinical, neuroimaging, biochemical, and molecular genetic features. DNA samples were used for targeted direct sequencing, targeted next-generation sequencing, or whole exome sequencing. RESULTS: There were 51 patients in the Pediatric Genetic Movement Disorder Clinic. Twenty-five patients had dystonia, 27 patients had ataxia, 7 patients had chorea-athetosis, 8 patients had tremor, and 7 patients had hyperkinetic movements. A genetic diagnosis was confirmed in 26 patients, including in 20 patients with ataxia and 6 patients with dystonia. Targeted next-generation sequencing panels confirmed a genetic diagnosis in 9 patients, and whole exome sequencing identified a genetic diagnosis in 14 patients. CONCLUSIONS: We report a genetic diagnosis in 26 (51%) patients with pediatric movement disorders seen in a single Pediatric Genetic Movement Disorder Clinic. A genetic diagnosis provided either disease-specific treatment or effected management in 10 patients with a genetic diagnosis, highlighting the importance of early and specific diagnosis.
ABSTRACT
BACKGROUND: Likely pathogenic variants in SLC17A5 results in allelic disorders of free sialic acid metabolism including (1) infantile free sialic acid storage disease with severe global developmental delay, coarse facial features, hepatosplenomegaly, and cardiomegaly; (2) intermediate severe Salla disease with moderate to severe global developmental delay, hypotonia, and hypomyelination with or without coarse facial features, and (3) Salla disease with normal appearance, mild cognitive dysfunction, and spasticity. PATIENT DESCRIPTION: This five-year-old girl presented with infantile-onset severe global developmental delay, truncal hypotonia, and generalized dystonia following normal development during her first six months of life. Brain magnetic resonance imaging showed marked hypomyelination and a thin corpus callosum at age 19 months, both unchanged on follow-up at age 28 months. Urine free sialic acid was moderately elevated. Cerebrospinal fluid free sialic acid was marginally elevated. Sequencing of SLC17A5 revealed compound heterozygous likely pathogenic variants, namely, a known missense (c.291G>A) variant and a novel truncating (c.819+1G>A) variant, confirming the diagnosis of Salla disease at age 3.5 years. CONCLUSION: We report a new patient with intermediate severe Salla disease. Normal or marginally elevated urine or cerebrospinal fluid free sialic acid levels cannot exclude Salla disease. In patients with progressive global developmental delay and hypomyelination on brain magnetic resonance imaging, Salla disease should be included into the differential diagnosis.
Subject(s)
Sialic Acid Storage Disease/complications , Sialic Acid Storage Disease/diagnosis , Child, Preschool , Corpus Callosum/diagnostic imaging , Databases, Bibliographic/statistics & numerical data , Female , Humans , Magnetic Resonance Imaging , Mutation/genetics , Olivopontocerebellar Atrophies/complications , Olivopontocerebellar Atrophies/diagnostic imaging , Organic Anion Transporters/genetics , Sialic Acid Storage Disease/genetics , Symporters/geneticsABSTRACT
BACKGROUND AND HYPOTHESIS: Pyridoxine dependent epilepsy (PDE) due to mutations in the ALDH7A1 gene (PDE-ALDH7A1) is caused by α-aminoadipic-semialdehyde-dehydrogenase enzyme deficiency in the lysine pathway resulting in the accumulation of α-aminoadipic acid semialdehyde (α-AASA). Classical presentation is neonatal intractable seizures with a dramatic response to pyridoxine. Pyridoxine therapy does not prevent developmental delays in the majority of the patients. We hypothesized that L-arginine supplementation will decrease accumulation of α-AASA by competitive inhibition of lysine transport into the central nervous system and improve neurodevelopmental and neurocognitive functions in PDE-ALDH7A1. METHODS: A 12-year-old male with PDE-ALDH7A1 was treated with l-arginine supplementation as an innovative therapy. Treatment outcome was monitored by cerebral-spinal-fluid (CSF) α-AASA measurements at baseline, 6th and 12th months of therapy. Neuropsychological assessments were performed at baseline and 12th months of therapy. RESULTS: L-arginine therapy was well tolerated without side effects. CSF α-AASA was decreased 57% at 12th months of therapy. Neuropsychological assessments revealed improvements in general abilities index from 108 to 116 and improvements in verbal and motor functioning at 12th months of therapy. CONCLUSION: The short-term treatment outcome of this novel L-arginine supplementation therapy for PDE-ALDH7A1 was successful for biochemical and neurocognitive improvements.