RESUMEN
OBJECTIVE: To determine whether pharmacologic treatment for neonatal abstinence syndrome (NAS) is associated with changes in DNA methylation (DNAm) of the mu-opioid receptor gene (OPRM1) and improvements in neonatal neurobehavior. STUDY DESIGN: Buccal swabs were collected from 37 neonates before and after morphine treatment for NAS. Genomic DNA was extracted, and DNAm was examined at 4 cytosine-phosphate-guanine (CpG) sites within the OPRM1 gene. Assessment with the NICU Network Neurobehavioral Scales (NNNS) was also performed before and after NAS treatment. Changes in DNAm (DNAmpost-tx - DNAmpre-tx) and NNNS summary scores (NNNSpost-tx - NNNSpre-tx) were then calculated. Path analysis was used to examine associations among pharmacologic treatment (length of treatment [LOT] and total dose of morphine), changes in DNAm, and changes in NNNS summary scores. RESULTS: DNAm was significantly decreased from pretreatment to post-treatment at 1 of 4 CpG sites within the OPRM1 gene. Neonates also demonstrated decreased excitability, hypertonia, lethargy, signs of stress and abstinence, and increased quality of movement and regulation from pretreatment to post-treatment. Longer LOT and higher morphine dose were associated with greater decreases in DNAm; greater decreases in DNAm were associated with greater decreases in excitability and hypertonia on the NNNS. CONCLUSIONS: Pharmacologic treatment of NAS is associated with decreased DNAm of the OPRM1 gene and improved neonatal neurobehavior. Epigenetic changes may play a role in these changes in neonatal neurobehavior.
Asunto(s)
Síndrome de Abstinencia Neonatal , Metilación de ADN , Humanos , Recién Nacido , Morfina/uso terapéutico , Hipertonía Muscular/tratamiento farmacológico , Hipertonía Muscular/genética , Síndrome de Abstinencia Neonatal/diagnóstico , Síndrome de Abstinencia Neonatal/tratamiento farmacológico , Síndrome de Abstinencia Neonatal/genética , Estudios ProspectivosRESUMEN
Partial monosomy 21 results in a great variability of clinical features that may be associated with the size and location of the deletion. In this study, we report a 22-month-old girl who showed a 45,XX,add(12)(p13)dn,-21 karyotype. The final cytogenomic result was 45,XX,der(12)t(12;21)(p13;q22.11) dn,-21.arr[hg19] 21q11.2q22.11(14824453_33868129)×1 revealing a deletion from 21pter to 21q22.11. Clinical manifestation of the patient included hypertonia, a long philtrum, epicanthic folds, low-set ears, and café-au-lait macules - a phenotype considered as mild despite the relatively large size of the deletion compared to patients from the literature.
Asunto(s)
Anomalías Múltiples/genética , Manchas Café con Leche/genética , Deleción Cromosómica , Cromosomas Humanos Par 21/ultraestructura , Cara/anomalías , Hipertonía Muscular/genética , Cromosomas Humanos Par 21/genética , Discapacidades del Desarrollo/genética , Femenino , Pérdida Auditiva Bilateral/genética , Humanos , Recién Nacido , Cariotipificación , Fenotipo , Escoliosis/genéticaRESUMEN
Distal arthrogryposis (DA) is a feature in genetically and clinically heterogeneous groups of disorders. Mostly myopathic and neurogenic defects have been described, but many patients remain without genetic diagnosis. We are elaborating on the clinical presentation of neonatal cases with DA who carry novel mutations in the nonselective sodium leak channel (NALCN). Two patients reported herein were remarkable for central hypertonicity in addition to DA. By trio-whole exome sequencing, two undescribed de novo mutations in NALCN were revealed. Both mutations (p.F317C and p.V595F) are located on pore-forming segments of NALCN. Dominant NALCN mutations in the pore-forming segments have been identified in similar patients, whereas recessive mutations outside the pore-forming segments result in different phenotypes. Our findings with central hypertonia broaden the phenotypic spectrum of de novo mutations in the pore-forming segments of NALCN. Recent findings of successful acetazolamide treatment in patients with channelopathies might point to potential therapies based on the ion channel similarities and the location of the mutation.
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Disostosis Craneofacial/genética , Hipertonía Muscular/genética , Canales de Sodio/genética , Encéfalo/diagnóstico por imagen , Disostosis Craneofacial/complicaciones , Disostosis Craneofacial/diagnóstico , Disostosis Craneofacial/diagnóstico por imagen , Femenino , Humanos , Recién Nacido , Recien Nacido Prematuro , Canales Iónicos , Imagen por Resonancia Magnética , Proteínas de la Membrana , Hipertonía Muscular/complicaciones , Hipertonía Muscular/diagnóstico , Radiografía TorácicaRESUMEN
Glycinergic neurotransmission is a major inhibitory influence in the CNS and its disruption triggers a paediatric and adult startle disorder, hyperekplexia. The postsynaptic α(1)-subunit (GLRA1) of the inhibitory glycine receptor (GlyR) and the cognate presynaptic glycine transporter (SLC6A5/GlyT2) are well-established genes of effect in hyperekplexia. Nevertheless, 52% of cases (117 from 232) remain gene negative and unexplained. Ligand-gated heteropentameric GlyRs form chloride ion channels that contain the α(1) and ß-subunits (GLRB) in a 2α(1):3ß configuration and they form the predominant population of GlyRs in the postnatal and adult human brain, brainstem and spinal cord. We screened GLRB through 117 GLRA1- and SLC6A5-negative hyperekplexia patients using a multiplex-polymerase chain reaction and Sanger sequencing approach. The screening identified recessive and dominant GLRB variants in 12 unrelated hyperekplexia probands. This primarily yielded homozygous null mutations, with nonsense (n = 3), small indel (n = 1), a large 95 kb deletion (n = 1), frameshifts (n = 1) and one recurrent splicing variant found in four cases. A further three cases were found with two homozygous and one dominant GLRB missense mutations. We provide strong evidence for the pathogenicity of GLRB mutations using splicing assays, deletion mapping, cell-surface biotinylation, expression studies and molecular modelling. This study describes the definitive assignment of GLRB as the third major gene for hyperekplexia and impacts on the genetic stratification and biological causation of this neonatal/paediatric disorder. Driven principally by consanguineous homozygosity of GLRB mutations, the study reveals long-term additive phenotypic outcomes for affected cases such as severe apnoea attacks, learning difficulties and developmental delay.
Asunto(s)
Epilepsia/genética , Enfermedades Genéticas Ligadas al Cromosoma X/genética , Hipertonía Muscular/genética , Receptores de Glicina/genética , Reflejo Anormal/genética , Adolescente , Adulto , Secuencia de Aminoácidos , Niño , Preescolar , Epilepsia/fisiopatología , Femenino , Enfermedades Genéticas Ligadas al Cromosoma X/fisiopatología , Predisposición Genética a la Enfermedad , Proteínas de Transporte de Glicina en la Membrana Plasmática/genética , Proteínas de Transporte de Glicina en la Membrana Plasmática/metabolismo , Homocigoto , Humanos , Masculino , Datos de Secuencia Molecular , Hipertonía Muscular/fisiopatología , Mutación , Linaje , Conformación Proteica , Sitios de Empalme de ARN/genética , Receptores de Glicina/química , Receptores de Glicina/metabolismo , Relación Estructura-ActividadRESUMEN
Intellectual disability (ID) is estimated to affect 1-3% of the general population and is a common reason for referrals to pediatric and adult geneticists, as well as neurologists. There are many genetic and non-genetic causes of ID; X-linked forms are identifiable through their characteristic inheritance pattern. Current testing methods have been able to identify over 100 genes on the X chromosome responsible for X-linked intellectual disability (XLID) syndromes. MED12 [MIM *300188] (mediator complex subunit 12) mutations have been linked to numerous XLID syndromes, including Lujan, FG, and Ohdo, and MED12 is included in many XLID panels. MED12 is located at Xq13.1 and its product has roles in transcriptional activation and repression. We describe two affected male siblings and their unaffected mother with a novel missense mutation in MED12, c.4147G>A (p.Ala1383Thr). The siblings share some features of Ohdo syndrome, including feeding difficulties, microcephaly, and speech delay. However, additional attributes such as hypertonia, eosinophilic esophagitis, penile chordee, and particular facial dysmorphisms depart sufficiently from individuals previously described such that they appear to represent a new and expanded phenotype. This case lends credence to the evolving theory that the subtypes of Ohdo, and perhaps other MED12 disorders, reflect a spectrum of characteristics, rather than distinct syndromes. As XLID panel testing and whole exome sequencing (WES) becomes a standard of care for affected males, further MED12 mutations will broaden the phenotype of these intriguing disorders and challenge clinicians to rethink the current diagnostic boundaries.
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Anomalías Múltiples/genética , Blefarofimosis/genética , Blefaroptosis/genética , Anomalías Craneofaciales/genética , Esofagitis Eosinofílica/genética , Genes Ligados a X/genética , Cardiopatías Congénitas/genética , Discapacidad Intelectual/genética , Complejo Mediador/genética , Hipertonía Muscular/genética , Atrofia Muscular/genética , Mutación Missense/genética , Anomalías Múltiples/patología , Adulto , Blefarofimosis/patología , Blefaroptosis/patología , Niño , Anomalías Craneofaciales/patología , Esofagitis Eosinofílica/patología , Cardiopatías Congénitas/patología , Humanos , Lactante , Discapacidad Intelectual/patología , Masculino , Hipertonía Muscular/patología , Atrofia Muscular/patología , Fenotipo , PronósticoRESUMEN
Hypertonia, which results from motor pathway defects in the central nervous system (CNS), is observed in numerous neurological conditions, including cerebral palsy, stroke, spinal cord injury, stiff-person syndrome, spastic paraplegia, dystonia and Parkinson disease. Mice with mutation in the hypertonic (hyrt) gene exhibit severe hypertonia as their primary symptom. Here we show that hyrt mutant mice have much lower levels of gamma-aminobutyric acid type A (GABA(A)) receptors in their CNS, particularly the lower motor neurons, than do wild-type mice, indicating that the hypertonicity of the mutants is likely to be caused by deficits in GABA-mediated motor neuron inhibition. We cloned the responsible gene, trafficking protein, kinesin binding 1 (Trak1), and showed that its protein product interacts with GABA(A) receptors. Our data implicate Trak1 as a crucial regulator of GABA(A) receptor homeostasis and underscore the importance of hyrt mice as a model for studying the molecular etiology of hypertonia associated with human neurological diseases.
Asunto(s)
Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Homeostasis , Hipertonía Muscular/metabolismo , Mutación/genética , Receptores de GABA-A/metabolismo , Proteínas Adaptadoras del Transporte Vesicular , Animales , Células del Asta Anterior/patología , Cromosomas de los Mamíferos/genética , Diazepam/farmacología , Electromiografía , Expresión Génica , Homocigoto , Humanos , Cuerpos de Inclusión/patología , Cuerpos de Inclusión/ultraestructura , Ratones , Datos de Secuencia Molecular , Hipertonía Muscular/genética , Hipertonía Muscular/patología , Músculo Esquelético/efectos de los fármacos , Mapeo Físico de Cromosoma , Puente/patología , Puente/ultraestructura , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
Myostatin, a member of the transforming growth factor ß family, is a potent negative regulator of skeletal muscle growth, as myostatin-deficient mice show a great increase in muscle mass. Yet the physical performance of these animals is reduced. As an explanation for this, alterations in the steps in excitation-contraction coupling were hypothesized and tested for in mice with the 12 bp deletion in the propeptide region of the myostatin precursor (Mstn(Cmpt-dl1Abc) or Cmpt). In voluntary wheel running, control C57BL/6 mice performed better than the mutant animals in both maximal speed and total distance covered. Despite the previously described lower specific force of Cmpt animals, the pCa-force relationship, determined on chemically permeabilized fibre segments, did not show any significant difference between the two mouse strains. While resting intracellular Ca(2+) concentration ([Ca(2+)]i) measured on single intact flexor digitorum brevis (FDB) muscle fibres using Fura-2 AM was similar to control (72.0 ± 1.7 vs. 78.1 ± 2.9 nM, n = 38 and 45), the amplitude of KCl-evoked calcium transients was smaller (360 ± 49 vs. 222 ± 45 nM, n = 22) in the mutant strain. Similar results were obtained using tetanic stimulation and Rhod-2 AM, which gave calcium transients that were smaller (2.42 ± 0.11 vs. 2.06 ± 0.10 ΔF/F0, n = 14 and 13, respectively) on Cmpt mice. Sarcoplasmic reticulum (SR) calcium release flux calculated from these transients showed a reduced peak (23.7 ± 3.0 vs. 15.8 ± 2.1 mM s(-1)) and steady level (5.7 ± 0.7 vs. 3.7 ± 0.5 mM s(-1)) with no change in the peak-to-steady ratio. The amplitude and spatial spread of calcium release events detected on permeabilized FDB fibres were also significantly smaller in mutant mice. These results suggest that reduced SR calcium release underlies the reduced muscle force in Cmpt animals.
Asunto(s)
Señalización del Calcio/genética , Hipertonía Muscular/genética , Mutación , Miostatina/genética , Animales , Señalización del Calcio/fisiología , Potenciales Evocados , Acoplamiento Excitación-Contracción/genética , Acoplamiento Excitación-Contracción/fisiología , Potenciales de la Membrana , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Fibras Musculares Esqueléticas/fisiología , Hipertonía Muscular/fisiopatología , Miostatina/fisiologíaRESUMEN
Homozygous frameshift BRAT1 mutations were found in patients with lethal neonatal rigidity and multifocal seizure syndrome (MIM# 614498). Here, we report on two siblings with compound heterozygous mutations in BRAT1. They had intractable seizures from neonatal period, dysmorphic features and hypertonia. Progressive microcephaly was also observed. Initial electroencephalogram showed a suppression-burst pattern, leading to a diagnosis of Ohtahara syndrome. They both died from pneumonia at 1 year and 3 months, respectively. Whole-exome sequencing of one patient revealed a compound heterozygous BRAT1 mutations (c.176T>C (p.Leu59Pro) and c.962_963del (p.Leu321Profs*81)). We are unable to obtain DNA from another patient. The p.Leu59Pro mutation occurred at an evolutionarily conserved amino acid in a CIDE-N (N-terminal of an cell death-inducing DFF45-like effector) domain, which has a regulatory role in the DNA fragmentation pathway of apoptosis. Our results further support that mutations of BRAT1 could lead to epileptic encephalopathy.
Asunto(s)
Epilepsia/genética , Microcefalia/genética , Hipertonía Muscular/genética , Proteínas Nucleares/genética , Epilepsia/fisiopatología , Femenino , Mutación del Sistema de Lectura , Heterocigoto , Humanos , Lactante , Recién Nacido , Masculino , Microcefalia/mortalidad , Microcefalia/fisiopatología , Hipertonía Muscular/mortalidad , Hipertonía Muscular/fisiopatología , HermanosRESUMEN
RATIONALE: Allan-Herndon-Dudley syndrome (AHDS) results from a pathogenic variant in the hemizygous subunit of the SLC16A2 gene, which encodes monocarboxylate transporter 8 and follows an X-linked recessive pattern. AHDS manifests as neuropsychomotor developmental delay, intellectual disability, movement disorders, and thyroid hormone abnormalities. It is frequently misdiagnosed as cerebral palsy or hypothyroidism. PATIENT CONCERNS: A 9-month-old male infant exhibited poor head control, hypodynamia, motor retardation, hypertonic limbs, and thyroid abnormalities. Despite levothyroxine supplementation and rehabilitation therapy, no improvements were observed. Whole-exome sequencing identified a novel nonsense mutation in SLC16A2 (c.124Gâ >â T, p.E42X), which unequivocally established the diagnosis. DIAGNOSES: AHDS was confirmed. INTERVENTIONS: Levothyroxine treatment commenced early in infancy, followed by 3 months of rehabilitation therapy, starting at 5 months of age. The combined administration of levothyroxine and methimazole was initiated at 1 year and 10 months of age, respectively. OUTCOMES: While improvements were noted in thyroid hormone levels, neurological developmental delays persisted. LESSONS: AHDS should be considered in patients presenting with atypical neurological features and thyroid hormone abnormalities such as elevated triiodothyronine and decreased thyroxine levels. The early utilization of exome sequencing aids in prompt diagnosis. The identified SLC16A2 nonsense mutation correlates with severe neurological phenotypes and adds to the spectrum of genetic variations associated with AHDS.
Asunto(s)
Codón sin Sentido , Transportadores de Ácidos Monocarboxílicos , Hipotonía Muscular , Atrofia Muscular , Simportadores , Humanos , Masculino , Transportadores de Ácidos Monocarboxílicos/genética , Lactante , Hipotonía Muscular/genética , Hipotonía Muscular/diagnóstico , Simportadores/genética , Atrofia Muscular/genética , Atrofia Muscular/diagnóstico , Fenotipo , Discapacidad Intelectual Ligada al Cromosoma X/genética , Discapacidad Intelectual Ligada al Cromosoma X/diagnóstico , Tiroxina/uso terapéutico , Hipertonía Muscular/genética , Hipertonía Muscular/diagnóstico , Secuenciación del Exoma/métodosRESUMEN
Startle disease is a rare, potentially fatal neuromotor disorder characterized by exaggerated startle reflexes and hypertonia in response to sudden unexpected auditory, visual or tactile stimuli. Mutations in the GlyR α(1) subunit gene (GLRA1) are the major cause of this disorder, since remarkably few individuals with mutations in the GlyR ß subunit gene (GLRB) have been found to date. Systematic DNA sequencing of GLRB in individuals with hyperekplexia revealed new missense mutations in GLRB, resulting in M177R, L285R and W310C substitutions. The recessive mutation M177R results in the insertion of a positively-charged residue into a hydrophobic pocket in the extracellular domain, resulting in an increased EC(50) and decreased maximal responses of α(1)ß GlyRs. The de novo mutation L285R results in the insertion of a positively-charged side chain into the pore-lining 9' position. Mutations at this site are known to destabilize the channel closed state and produce spontaneously active channels. Consistent with this, we identified a leak conductance associated with spontaneous GlyR activity in cells expressing α(1)ß(L285R) GlyRs. Peak currents were also reduced for α(1)ß(L285R) GlyRs although glycine sensitivity was normal. W310C was predicted to interfere with hydrophobic side-chain stacking between M1, M2 and M3. We found that W310C had no effect on glycine sensitivity, but reduced maximal currents in α(1)ß GlyRs in both homozygous (α(1)ß(W310C)) and heterozygous (α(1)ßß(W310C)) stoichiometries. Since mild startle symptoms were reported in W310C carriers, this may represent an example of incomplete dominance in startle disease, providing a potential genetic explanation for the 'minor' form of hyperekplexia.
Asunto(s)
Hipertonía Muscular/genética , Mutación Missense , Receptores de Glicina/genética , Reflejo Anormal/genética , Reflejo de Sobresalto/genética , Femenino , Humanos , Masculino , Análisis de Secuencia de ADNRESUMEN
BACKGROUND: Myostatin, a member of the TGFß superfamily, is well known as a potent and specific negative regulator of muscle growth. Targeting the myostatin signalling pathway may offer promising therapeutic strategies for the treatment of muscle-wasting disorders. In the last decade, various myostatin-binding proteins have been identified to be able to inhibit myostatin activity. One of these is GASP1 (Growth and Differentiation Factor-Associated Serum Protein-1), a protein containing a follistatin domain as well as multiple domains associated with protease inhibitors. Despite in vitro data, remarkably little is known about in vivo functions of Gasp1. To further address the role of GASP1 during mouse development and in adulthood, we generated a gain-of-function transgenic mouse model that overexpresses Gasp1 under transcriptional control of the human cytomegalovirus immediate-early promoter/enhancer. RESULTS: Overexpression of Gasp1 led to an increase in muscle mass observed not before day 15 of postnatal life. The surGasp1 transgenic mice did not display any other gross abnormality. Histological and morphometric analysis of surGasp1 rectus femoris muscles revealed an increase in myofiber size without a corresponding increase in myofiber number. Fiber-type distribution was unaltered. Interestingly, we do not detect a change in total fat mass and lean mass. These results differ from those for myostatin knockout mice, transgenic mice overexpressing the myostatin propeptide or follistatin which exhibit both muscle hypertrophy and hyperplasia, and show minimal fat deposition. CONCLUSIONS: Altogether, our data give new insight into the in vivo functions of Gasp1. As an extracellular regulatory factor in the myostatin signalling pathway, additional studies on GASP1 and its homolog GASP2 are required to elucidate the crosstalk between the different intrinsic inhibitors of the myostatin.
Asunto(s)
Proteínas Portadoras/genética , Fibras Musculares Esqueléticas/fisiología , Hipertonía Muscular/genética , Miostatina/metabolismo , Músculo Cuádriceps/fisiología , Animales , Antígenos Virales/genética , Proteínas Portadoras/biosíntesis , Citomegalovirus/genética , Folistatina/genética , Folistatina/metabolismo , Regulación de la Expresión Génica , Proteínas Inmediatas-Precoces/genética , Péptidos y Proteínas de Señalización Intracelular , Ratones , Ratones Transgénicos , Hipertonía Muscular/metabolismo , Miostatina/genética , Fenotipo , Regiones Promotoras Genéticas , ARN Mensajero/biosíntesis , Transcripción GenéticaRESUMEN
Episodic falling syndrome (EFS) is a canine paroxysmal hypertonicity disorder found in Cavalier King Charles spaniels. Episodes are triggered by exercise, stress or excitement and characterized by progressive hypertonicity throughout the thoracic and pelvic limbs, resulting in a characteristic 'deer-stalking' position and/or collapse. We used a genome-wide association strategy to map the EFS locus to a 3.48 Mb critical interval on canine chromosome 7. By prioritizing candidate genes on the basis of biological plausibility, we found that a 15.7 kb deletion in BCAN, encoding the brain-specific extracellular matrix proteoglycan brevican, is associated with EFS. This represents a compelling causal mutation for EFS, since brevican has an essential role in the formation of perineuronal nets governing synapse stability and nerve conduction velocity. Mapping of the deletion breakpoint enabled the development of Multiplex PCR and Multiplex Ligation-dependent Probe Amplification (MLPA) genotyping tests that can accurately distinguish normal, carrier and affected animals. Wider testing of a larger population of CKCS dogs without a history of EFS from the USA revealed that carriers are extremely common (12.9%). The development of molecular genetic tests for the EFS microdeletion will allow the implementation of directed breeding programs aimed at minimizing the number of animals with EFS and enable confirmatory diagnosis and pharmacotherapy of affected dogs.
Asunto(s)
Brevicano/genética , Enfermedades de los Perros/genética , Genotipo , Hipertonía Muscular/veterinaria , Animales , Cruzamiento , Perros , Eliminación de Gen , Estudio de Asociación del Genoma Completo , Hipertonía Muscular/genéticaRESUMEN
Hyperekplexia is a rare, but potentially fatal, neuromotor disorder characterized by exaggerated startle reflexes and hypertonia in response to sudden, unexpected auditory or tactile stimuli. This disorder is primarily caused by inherited mutations in the genes encoding the glycine receptor (GlyR) alpha1 subunit (GLRA1) and the presynaptic glycine transporter GlyT2 (SLC6A5). In this study, systematic DNA sequencing of GLRA1 in 88 new unrelated human hyperekplexia patients revealed 19 sequence variants in 30 index cases, of which 21 cases were inherited in recessive or compound heterozygote modes. This indicates that recessive hyperekplexia is far more prevalent than previous estimates. From the 19 GLRA1 sequence variants, we have investigated the functional effects of 11 novel and 2 recurrent mutations. The expression levels and functional properties of these hyperekplexia mutants were analyzed using a high-content imaging system and patch-clamp electrophysiology. When expressed in HEK293 cells, either as homomeric alpha1 or heteromeric alpha1beta GlyRs, subcellular localization defects were the major mechanism underlying recessive mutations. However, mutants without trafficking defects typically showed alterations in the glycine sensitivity suggestive of disrupted receptor function. This study also reports the first hyperekplexia mutation associated with a GlyR leak conductance, suggesting tonic channel opening as a new mechanism in neuronal ligand-gated ion channels.
Asunto(s)
Hipertonía Muscular/genética , Receptores de Glicina/genética , Reflejo Anormal/genética , Reflejo de Sobresalto/genética , Línea Celular , Femenino , Variación Genética , Humanos , Masculino , Mutación/genética , Fenotipo , TransfecciónRESUMEN
Hyperekplexia is characterised by neonatal hypertonia and an exaggerated startle reflex in response to acoustic or tactile stimuli. Genetic analysis of this disorder has revealed mutations in genes for several postsynaptic proteins involved in glycinergic neurotransmission, including the glycine receptor (GlyR) alpha1 and beta subunits, gephyrin and collybistin. However, new research suggests that mutations in the gene encoding the presynaptic glycine transporter GlyT2 are a second major cause of human hyperekplexia, as well as congenital muscular dystonia type 2 (CMD2) in cattle. These findings raise the intriguing possibility that both presynaptic and postsynaptic causes of disease might also exist in related disorders, such as idiopathic generalised epilepsies, where mutations in inhibitory GABA(A) receptor subunit genes have already been identified.
Asunto(s)
Hipertonía Muscular/genética , Reflejo de Sobresalto/genética , Animales , Pruebas Genéticas , Glicina/metabolismo , Salud , Humanos , Receptores de Glicina/química , Receptores de Glicina/genética , Receptores de Glicina/metabolismo , Sinapsis/metabolismoRESUMEN
Hyperekplexia is a rare disorder caused by autosomal dominant or recessive modes of inheritance and characterized by episodes of exaggerated startle. Five causative genes have been identified to date. The syndrome has been recognized for decades and due to its rarity, the literature contains mostly descriptive reports, many early studies lacking molecular genetic diagnoses. A spectrum of clinical severity exists. Severe cases can lead to neonatal cardiac arrest and death during an episode, an outcome prevented by early diagnosis and clinical vigilance. Large treatment studies are not feasible, so therapeutic measures continue to be empiric. A marked response to clonazepam is often reported but refractory cases exist. Herein we report the clinical course and treatment response of a severely affected infant homozygous for an SLC6A5 nonsense mutation and review the literature summarizing the history and genetic understanding of the disease as well as the described comorbidities and treatment options.
Asunto(s)
Hipertonía Muscular , Fenotipo , Adulto , Anticonvulsivantes/uso terapéutico , Discapacidades del Desarrollo/epidemiología , Discapacidades del Desarrollo/genética , Trastornos de Alimentación y de la Ingestión de Alimentos/epidemiología , Trastornos de Alimentación y de la Ingestión de Alimentos/genética , Femenino , Pruebas Genéticas , Humanos , Lactante , Hipertonía Muscular/epidemiología , Hipertonía Muscular/genética , Hipertonía Muscular/terapia , Receptores de Glicina/genética , Reflejo Anormal/genética , Síndromes de la Apnea del Sueño/epidemiología , Síndromes de la Apnea del Sueño/genéticaRESUMEN
Neonatal Schwartz-Jampel syndrome type II is a rare and severe form of genetic disorder. Different from the classical appearance in infancy, neonatal presentation involves respiratory and feeding difficulties, along with characteristic pursed appearance of the mouth, myotonia, skeletal dysplasia and severe fatal hyperthermia. The clinical spectrum of this syndrome is so wide that it easily baffles with more common differentials. In this case report, a neonate born to third-degree consanguineous marriage with previous two abortions presented with respiratory difficulty, severe hyperthermia and feeding difficulty, which were daunting challenges to manage due to being refractory to standard line of management. Severe myotonia and gross dysmorphism were challenging dots to connect. Targeted exome sequencing was a ray of hope, which revealed homozygous mutation in the leukaemia inhibitory factor receptor gene on chromosome 5p13, confirming the genetic diagnosis for a fairly common spectrum of symptoms. The neonate later developed pneumoperitoneum and succumbed to underlying severe neonatal illness.
Asunto(s)
Osteocondrodisplasias , Consanguinidad , Cara , Femenino , Humanos , Recién Nacido , Hipertonía Muscular/diagnóstico , Hipertonía Muscular/genética , Mutación , Osteocondrodisplasias/complicaciones , Osteocondrodisplasias/diagnóstico , Osteocondrodisplasias/genética , EmbarazoRESUMEN
The neuronal ceroid lipofuscinoses (NCLs) are autosomal recessively inherited disorders collectively considered to be one among the most common pediatric neurodegenerative lysosomal storage diseases. Four main clinical subtypes have been described based on the age at presentation: infantile, late infantile, juvenile and adult types. In addition, rare congenital cases of NCL have been reported in the literature. Previously, a homozygous mutation in the cathepsin D gene has been shown to cause congenital NCL in a patient of Pakistani origin. We report a case of a 39-week estimated gestational age female infant with severe microcephaly and hypertonia, whereas MRI showed generalized hypoplasia of the cerebral and cerebellar hemispheres. The infant died on day two after birth. Postmortem examination revealed a small, firm brain with extensive neuronal loss and gliosis. Remaining neurons, astrocytes and macrophages contained PAS-positive storage material with granular ultrastructure and immunoreactivity against sphingolipid activator protein D. A diagnosis of congenital NCL was rendered with a novel mutation, c.299C > T (p.Ser100Phe) in exon 3 of the cathepsin D gene. In the patient fibroblasts, cathepsin D activity was marginal, but the protein appeared stable and normally processed. This was confirmed in overexpression studies. Importantly, by identification of the mutation in the family, we were able to confirm the first prenatal diagnosis excluding cathepsin D deficiency in the younger sibling of the patient.
Asunto(s)
Catepsina D/deficiencia , Catepsina D/genética , Muestra de la Vellosidad Coriónica , Lipofuscinosis Ceroideas Neuronales/genética , Adulto , Astrocitos/química , Astrocitos/ultraestructura , Encéfalo/patología , Química Encefálica , Muerte Celular , Femenino , Fibroblastos/enzimología , Gliosis/genética , Gliosis/patología , Humanos , Recién Nacido , Macrófagos/química , Macrófagos/ultraestructura , Microcefalia/genética , Hipertonía Muscular/genética , Lipofuscinosis Ceroideas Neuronales/diagnóstico , Lipofuscinosis Ceroideas Neuronales/enzimología , Lipofuscinosis Ceroideas Neuronales/patología , Neuronas/ultraestructura , Mutación Puntual , Embarazo , Proteínas Activadoras de Esfingolípidos/análisisRESUMEN
Hyperekplexia (OMIM 149400) is an uncommon neurologic disorder characterized by exaggerated response to sensitive stimuli. It may be sporadic or familial. The disease is usually caused by mutations in the inhibitory glycine receptor alpha1-subunit. The authors report a male patient who is affected by the major form of familial hyperekplexia. He is currently 5 years old and is being successfully treated with clonazepam. Prenatal diagnosis was made owing to prior identification of point mutation K276E in his affected mother. Early diagnosis avoided complex and prolonged differential diagnostic procedures and allowed for early and effective intervention on severe neonatal symptoms: hypertonia, episodes of cyanosis, apneic spells, and massive myoclonic jerks. During his first year of life, the patient was treated with cycles of phenobarbital and diazepam and achieved partial clinical response. Subsequent therapy with low-dose clonazepam was highly effective in reducing myoclonic jerks and exaggerated startle reaction, and unlike previously used drugs, it was decisive in reducing hypertonia.
Asunto(s)
Anticonvulsivantes/uso terapéutico , Clonazepam/uso terapéutico , Salud de la Familia , Hipertonía Muscular , Diagnóstico Prenatal , Reflejo Anormal , Preescolar , Femenino , Ácido Glutámico/genética , Humanos , Lisina/genética , Masculino , Hipertonía Muscular/diagnóstico , Hipertonía Muscular/tratamiento farmacológico , Hipertonía Muscular/genética , Mutación Puntual , Embarazo , Receptores de Glicina/genéticaRESUMEN
We report two Japanese patients from two families with hyperekplexia who have a Arg271Gln mutation in the glycine receptor alpha 1 subunit gene. The clinical course of both patients was typical for hyperekplexia, characterized by neonatal hypertonia and exaggerated startle response, and which improved gradually with age. One was associated with umbilical hernia and hip dislocation, diagnosed at 11 months, while the other was diagnosed at 1 month. Both showed positive head retraction reflex. Four Japanese families have been reported as having hyperekplexia including our cases, of which three have shown the same missense Arg271Gln mutation, most frequently found in patients from Northern Europe and the United States.
Asunto(s)
Predisposición Genética a la Enfermedad/genética , Hipertonía Muscular/genética , Mutación Missense/genética , Receptores de Glicina/genética , Reflejo de Sobresalto/genética , Preescolar , Análisis Mutacional de ADN , Femenino , Glicina/metabolismo , Luxación Congénita de la Cadera/complicaciones , Humanos , Lactante , Japón , Hipertonía Muscular/metabolismo , Hipertonía Muscular/fisiopatología , Músculo Esquelético/inervación , Músculo Esquelético/fisiopatología , Inhibición Neural/genética , Linaje , Reflejo Anormal/genética , Transmisión Sináptica/genética , SíndromeRESUMEN
Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare autosomal recessive neuromuscular disorder caused by mutations in the IGHMBP2 gene and characterized by life-threatening respiratory distress due to irreversible diaphragmatic paralysis between 6weeks and 6months of age. In this study, we describe a two-month-old boy who presented with hypertonia at first and developed to hypotonia progressively, which was in contrast to the manifestations reported previously. Bone tissue compromise was also observed as one of the unique symptoms. Muscle biopsy indicated mild myogenic changes. He was misdiagnosed until genetic screening to be confirmed as SMARD1. SMARD1 is a clinical heterogeneous disease and this case broadens our perception of its phenotypes.