GABBR2 mutations determine phenotype in rett syndrome and epileptic encephalopathy.

OBJECTIVE: Rett syndrome (RTT) and epileptic encephalopathy (EE) are devastating neurodevelopmental disorders with distinct diagnostic criteria. However, highly heterogeneous and overlapping clinical features often allocate patients into the boundary of the two conditions, complicating accurate diagnosis and appropriate medical interventions. Therefore, we investigated the specific molecular mechanism that allows an understanding of the pathogenesis and relationship of these two conditions. METHODS: We screened novel genetic factors from 34 RTT-like patients without MECP2 mutations, which account for ∼90% of RTT cases, by whole-exome sequencing. The biological function of the discovered variants was assessed in cell culture and Xenopus tropicalis models. RESULTS: We identified a recurring de novo variant in GABAB receptor R2 (GABBR2) that reduces the receptor function, whereas different GABBR2 variants in EE patients possess a more profound effect in reducing receptor activity and are more responsive to agonist rescue in an animal model. INTERPRETATION: GABBR2 is a genetic factor that determines RTT- or EE-like phenotype expression depending on the variant positions. GABBR2-mediated γ-aminobutyric acid signaling is a crucial factor in determining the severity and nature of neurodevelopmental phenotypes. Ann Neurol 2017;82:466-478.

Noninvasive prenatal diagnosis of duchenne muscular dystrophy: comprehensive genetic diagnosis in carrier, proband, and fetus.

BACKGROUND: Noninvasive prenatal diagnosis of monogenic disorders using maternal plasma and targeted massively parallel sequencing is being investigated actively. We previously demonstrated that comprehensive genetic diagnosis of a Duchenne muscular dystrophy (DMD) patient is feasible using a single targeted sequencing platform. Here we demonstrate the applicability of this approach to carrier detection and noninvasive prenatal diagnosis. METHODS: Custom solution-based target enrichment was designed to cover the entire dystrophin (DMD) gene region. Targeted massively parallel sequencing was performed using genomic DNA from 4 mother and proband pairs to test whether carrier status could be detected reliably. Maternal plasma DNA at varying gestational weeks was collected from the same families and sequenced using the same targeted platform to predict the inheritance of the DMD mutation by their fetus. Overrepresentation of an inherited allele was determined by comparing the allele fraction of 2 phased haplotypes after examining and correcting for the recombination event. RESULTS: The carrier status of deletion/duplication and point mutations was detected reliably through using a single targeted massively parallel sequencing platform. Whether the fetus had inherited the DMD mutation was predicted correctly in all 4 families as early as 6 weeks and 5 days of gestation. In one of these, detection of the recombination event and reconstruction of the phased haplotype produced a correct diagnosis. CONCLUSIONS: Noninvasive prenatal diagnosis of DMD is feasible using a single targeted massively parallel sequencing platform with tiling design.

Mutational analysis of paediatric patients with tuberous sclerosis complex in Korea: genotype and epilepsy.

To date, only a few studies have reported that, in tuberous sclerosis, TSC2 mutations are more frequently associated with infantile spasms and cognitive impairment compared to TSC1 mutations. We analyzed the mutational spectrum of patients with tuberous sclerosis in Korea and attempted to explore the associations between genotype and seizure type/outcome. We performed mutational analyses on 70 unrelated patients with clinically confirmed tuberous sclerosis by using direct DNA sequencing and/or multiplex ligation-dependent probe amplification. The patients' medical records, including epilepsy type and outcome, were reviewed retrospectively. We identified pathogenic mutations in 55 patients (79%), 25 of which were novel. There were 12 TSC1 mutations and 43 TSC2 mutations. TSC1 mutations included 8 frameshift and 4 nonsense mutations. TSC2 mutations included 12 frameshift, 10 nonsense, 6 splicing, and 6 missense mutations, as well as 4 in-frame deletions and 5 large deletions. Fifty-eight patients had epilepsy (83%), including 19 patients with a history of infantile spasms. Compared to patients with TSC1 mutations, individuals with TSC2 mutations had a significantly higher frequency of epilepsy (p<0.05) and tended to have a higher frequency of infantile spasms (37% vs 17%; p<0.3). Most of the patients with TSC2 mutations who developed infantile spasms exhibited subsequent epilepsy (13/14; 93%). However, the presence/absence of infantile spasms did not influence seizure remission or cognitive outcome.

Electroencephalography in pediatric moyamoya disease: reappraisal of clinical value.

PURPOSE: The clinical value of electroencephalography (EEG) in pediatric moyamoya disease has been underestimated, though the characteristic patterns are well known. We undertook this study to evaluate the clinical value of EEG as a diagnostic and postoperative follow-up modality in pediatric moyamoya disease. METHODS: We retrospectively reviewed the pre and postoperative EEG with effective hyperventilation in 127 pediatric moyamoya patients and compared their patterns with hemodynamic images. RESULTS: One hundred and two patients (80.3 %) among 127 showed abnormal EEG findings before revascularization surgery. The typical rebuild-up phenomenon was observed in 82 (64.6 %) and localized build-up in 32 (25.2 %) without any significant clinical ischemic events during and after hyperventilation. The rebuild-up was observed more frequently in younger age groups (less than 13 years) and Suzuki stages III. The location of the rebuild-up distribution and asymmetric build-up was consistent with the area showing hemodynamic abnormalities on single photon emission computed tomography and/or perfusion magnetic resonance imaging. Postoperative follow-up EEGs were performed in 41 patients. Six patients with remaining rebuild-up in postoperative follow-up EEG showed poorer postoperative clinical outcomes. CONCLUSIONS: This study may reappraise EEG as an easy, safe, and adjunctive diagnostic and postoperative follow-up modality for evaluation of hemodynamic status and clinical outcome, especially in children with moyamoya disease.

Involuntary movement in pediatric moyamoya disease patients: consideration of pathogenetic mechanism using neuroimaging studies.

PURPOSE: Involuntary movement is a rare symptom of moyamoya disease (MMD). No consensus has been reached regarding its clinical features and pathogenetic mechanism. Therefore, pediatric MMD patients presenting with involuntary movement were retrospectively analyzed, focusing on the image findings. METHODS: A total of 513 patients who were treated for MMD were reviewed. After exclusion of MMD syndromes and those with accompanying conditions related to involuntary movements, five patients (mean age: 11.6 years, range: 5-13 years) were evaluated. RESULTS: All of the patients improved their symptoms rapidly after the indirect bypass operations to the contralateral hemisphere. All remained symptom-free during the long follow-up period. Comprehensive evaluation of the preoperative imaging findings failed to suggest a characteristic feature in common, corresponding to the existing hypotheses or a new hypothesis. Only one patient showed infarction preoperatively, and only one patient showed prominently enhanced collateral vessels in the basal ganglia. Although a decrease in vascular reserve was observed in all patients, the location and laterality were nonspecific. CONCLUSION: There still appears to be confusion regarding the pathogenetic mechanism of involuntary movement in MMD with no repetitive, established imaging features to explain the phenomenon. Nonetheless, with its excellent response to surgical treatment, clinical awareness of this rare symptom of MMD should be emphasized as a differential diagnosis for secondary movement disorder in children.

Rare coincidence of familial central core disease and hemophagocytic lymphohistiocytosis.

Central core disease is a congenital myopathy caused by mutations in RYR1. A 6-year-old girl was admitted due to difficulty in running and climbing stairs. Another 13 members through the four generations had similar symptoms, indicating autosomal dominant inheritance. Muscle biopsy showed the characteristic central cores in predominant type 1 fibers. She later developed hemophagocytic lymphohistiocytosis. Mutation analysis identified c.14582G>A in RYR1, and c.1693delG and c.2954 + 5G>A in UNC13D. To our knowledge, this is the first case of a patient with central core disease, carrying a RYR1 mutation in a Korean large family, who had concurrent familial hemophagocytic lymphohistiocytosis.

Effectiveness of intravenous levetiracetam as an adjunctive treatment in pediatric refractory status epilepticus.

OBJECTIVES: Intravenous levetiracetam (LEV) has been shown to be effective and safe in treating adults with refractory status epilepticus (SE). We sought to investigate the efficacy and safety of intravenous LEV for pediatric patients with refractory SE. METHODS: We performed a retrospective medical-record review of pediatric patients who were treated with intravenous LEV for refractory SE. Clinical information regarding age, sex, seizure type, and underlying neurological status was collected. We evaluated other anticonvulsants that were used prior to administration of intravenous LEV and assessed loading dose, response to treatment, and any adverse events from intravenous LEV administration. RESULTS: Fourteen patients (8 boys and 6 girls) received intravenous LEV for the treatment of refractory SE. The mean age of the patients was 4.4 ± 5.5 years (range, 4 days to 14.6 years). Ten of the patients were neurologically healthy prior to the refractory SE, and the other 4 had been previously diagnosed with epilepsy. The mean loading dose of intravenous LEV was 26 ± 4.6 mg/kg (range, 20-30 mg/kg). Seizure termination occurred in 6 (43%) of the 14 patients. In particular, 4 (57%) of the 7 patients younger than 2 years showed seizure termination. No immediate adverse events occurred during or after infusions. CONCLUSIONS: The current study demonstrated that the adjunctive use of intravenous LEV was effective and well tolerated in pediatric patients with refractory SE, even in patients younger than 2 years. Intravenous LEV should be considered as an effective and safe treatment option for refractory SE in pediatric patients.

Distinct neurological features in a patient with Schinzel-Giedion syndrome caused by a recurrent SETBP1 mutation.

INTRODUCTION: Schinzel-Giedion syndrome (SGS) is a rare multiple congenital malformation syndrome defined by characteristic facial features, profound developmental delay, severe growth failure, and multiple congenital anomalies. Most individuals affected by SGS die in early childhood mainly because of progressive neurodegeneration and respiratory failure. The causative gene of SGS, SETBP1, was identified, but there are few reports of SGS with molecular confirmation worldwide. PATIENT AND METHOD: In this study, we present a 10-month-old boy presenting with SGS complicated by epilepsy and profound developmental delay. RESULTS: Typical facial features, multiple anomalies, and associated neurological findings suggested a clinical diagnosis of SGS. Unusually in our patient, generalized tonic seizure occurred and has been controlled well by combined antiepileptic therapy during 7 months of follow-up. Electroencephalography findings were compatible with partial seizures, and ventriculomegaly, thinning of the corpus callosum, and delayed myelination were identified on brain MR images. SETBP1 mutational analysis revealed the presence of a recurrent mutation, p.Gly870Ser. Thus, the diagnosis of our patient was molecularly confirmed as SGS. CONCLUSIONS: Although this syndrome is extremely rare, it is important to consider SGS in the differential diagnosis of infantile-onset epilepsy with progressive neurodevelopmental retardation, especially in patients with multiple anomalies and facial dysmorphism.

Subclinical hypothyroidism during valproic acid therapy in children and adolescents with epilepsy.

The aim of this study was to evaluate the incidence of thyroid dysfunction during valproic acid (VPA) therapy in children and adolescents with epilepsy. The serum levels of thyroid-stimulating hormone (TSH), free thyroxine, and triiodothyronine were evaluated in 61 children with epilepsy who received VPA monotherapy for more than 6 months and in 144 controls. We analyzed the effect of age, seizure type, duration of VPA treatment, dose of VPA, and serum level of VPA on thyroid function. The incidence of subclinical hypothyroidism was significantly higher in patients with VPA therapy than in controls (52.4 vs. 16.7%; p < 0.001). In addition, of the 61 patients, 5 (8.1%) exhibited TSH levels that were >10 µIU/mL. However, none of the patients and controls showed overt hypothyroidism. Serum VPA level and daily dose of VPA were correlated with TSH level. Subclinical hypothyroidism developed frequently in children and adolescents during VPA therapy.

Paroxysmal nonepileptic events in pediatric patients confirmed by long-term video-EEG monitoring--Single tertiary center review of 143 patients.

The purpose of the study was to evaluate the clinical characteristics of paroxysmal nonepileptic events (PNEs) in pediatric patients. Reports of 1108 patients who underwent long-term video-EEG monitoring at Seoul National University Children's Hospital were reviewed retrospectively. One hundred forty-three (12.9%) patients were diagnosed as having PNEs. The most common type of PNE was staring. Staring, tonic posturing, sleep myoclonus, and sleep-related disorders were more common in patients younger than 6 years old. Psychogenic nonepileptic seizure was the most common PNE in patients older than 6 years. Patients who were younger than 6 years old showed shorter disease duration and more varied types of PNEs when compared to older patients (6 years old or older). Presence of epilepsy was not significantly related to clinical difference in PNEs. In patients with developmental delay, staring and tonic posture were significantly more frequent than patients without developmental delay. Thirty-two patients without concurrent epilepsy were misdiagnosed with epilepsy, and AEDs were discontinued after the correct diagnosis of PNEs. Whenever the diagnosis of paroxysmal abnormal behavior is uncertain, correct diagnosis should be made using long-term video-EEG monitoring, especially in younger pediatric patients and patients with developmental delay.

Genetic diagnosis of Duchenne and Becker muscular dystrophy using next-generation sequencing technology: comprehensive mutational search in a single platform.

BACKGROUND: Duchenne muscular dystrophy or Becker muscular dystrophy might be a suitable candidate disease for application of next-generation sequencing in the genetic diagnosis because the complex mutational spectrum and the large size of the dystrophin gene require two or more analytical methods and have a high cost. The authors tested whether large deletions/duplications or small mutations, such as point mutations or short insertions/deletions of the dystrophin gene, could be predicted accurately in a single platform using next-generation sequencing technology. METHODS: A custom solution-based target enrichment kit was designed to capture whole genomic regions of the dystrophin gene and other muscular-dystrophy-related genes. A multiplexing strategy, wherein four differently bar-coded samples were captured and sequenced together in a single lane of the Illumina Genome Analyser, was applied. The study subjects were 25 PATIENTS: 16 with deficient dystrophin expression without a large deletion/duplication and 9 with a known large deletion/duplication. RESULTS: Nearly 100% of the exonic region of the dystrophin gene was covered by at least eight reads with a mean read depth of 107. Pathogenic small mutations were identified in 15 of the 16 patients without a large deletion/duplication. Using these 16 patients as the standard, the authors' method accurately predicted the deleted or duplicated exons in the 9 patients with known mutations. Inclusion of non-coding regions and paired-end sequence analysis enabled accurate identification by increasing the read depth and providing information about the breakpoint junction. CONCLUSIONS: The current method has an advantage for the genetic diagnosis of Duchenne muscular dystrophy and Becker muscular dystrophy wherein a comprehensive mutational search may be feasible using a single platform.

Magnetoencephalography in pediatric lesional epilepsy surgery.

This study was performed to assess the usefulness of magnetoencephalography (MEG) as a presurgical evaluation modality in Korean pediatric patients with lesional localization-related epilepsy. The medical records and MEG findings of 13 pediatric patients (6 boys and 7 girls) with localization-related epilepsy, who underwent epilepsy surgery at Seoul National University Children's Hospital, were retrospectively reviewed. The hemispheric concordance rate was 100% (13/13 patients). The lobar or regional concordance rate was 77% (10/13 patients). In most cases, the MEG spike sources were clustered in the proximity of the lesion, either at one side of the margin (nine patients) or around the lesion (one patient); clustered spike sources were distant from the lesion in one patient. Among the patients with clustered spike sources near the lesion, further extensions (three patients) and distal scatters (three patients) were also observed. MEG spike sources were well lateralized and localized even in two patients without focal epileptiform discharges in the interictal scalp electroencephalography. Ten patients (77%) achieved Engel class I postsurgical seizure outcome. It is suggested that MEG is a safe and useful presurgical evaluation modality in pediatric patients with lesion localization-related epilepsy.

Pediatric moyamoya disease: An analysis of 410 consecutive cases.

OBJECTIVE: Moyamoya disease (MMD) is a cerebrovascular occlusive disease of the bilateral internal carotid arteries that causes a compensatory abnormal vascular network at the base of brain. The rare incidence and various surgical techniques applied have limited the clinical research on MMD. METHODS: We conducted a retrospective analysis of the surgical outcome of 410 pediatric MMD patients. All patients were treated in a relatively uniform scheme at a single institution. The surgical procedures consisted of bilateral encephaloduroarteriosynangiosis augmented by bifrontal encephalogaleo-/periosteal synangiosis. Logistic regression analyses were applied to reveal the prognostic factors for surgical outcome. RESULTS: The overall clinical outcome was excellent in 66%, good in 15%, fair in 15%, and poor in 4% of the patients. Therefore, 81% of the patients had a favorable clinical outcome (excellent and good). Multivariate analyses revealed that infarction on presentation was associated with unfavorable clinical outcome (odds ratio [OR], 2.85; 95% confidence interval [CI], 1.49-5.46; p < 0.01) and decreased vascular reserve only on single-photon emission computerized tomography (OR, 0.07; 95% CI, 0.01-0.52; p < 0.01), with favorable clinical outcome. INTERPRETATION: Our results indicate that an early diagnosis and active intervention before establishment of irreversible hemodynamic change are essential to achieve a favorable clinical outcome in children with MMD.

Relapsing demyelinating CNS disease in a Korean pediatric population: multiple sclerosis versus neuromyelitis optica.

BACKGROUND AND OBJECTIVE: Our objective was to characterize the clinical and radiologic features of Korean pediatric patients with relapsing central nervous system (CNS) demyelination disease. METHODS: Twenty-one patients with relapsing CNS demyelinating events were classified as having multiple sclerosis (MS, 18 patients) or neuromyelitis optica (NMO, three patients) according to the international consensus definitions. Retrospective analysis of clinical and radiologic features was conducted. Anti-aquaporin-4 antibody (AQP4 Ab) test was performed in six patients (including three NMO patients) who showed selective involvement of optic nerve and spinal cord. RESULTS: Median age at the initial episode in patients with MS was 7.0 years (range, 4.4-13.6 years). Three of 18 MS patients (3/18, 17%) showed selective involvement of the optic nerve and spinal cord during the clinical course. Five patients (31%) at the initial episode and nine patients (50%) at relapse met the McDonald magnetic resonance imaging criteria for dissemination in space. Oligoclonal bands detected with a silver staining method were positive in only one patient of 16 patients tested. Two NMO patients positive for AQP4 Ab showed frequent relapses and early disabilities that were unresponsive to interferon treatment. CONCLUSIONS: We conclude that Korean pediatric patients with relapsing CNS demyelination disease were characterized by preferential involvement of the optic nerve or spinal cord. The AQP4 Ab test seems to be useful for predicting clinical courses in the setting of heterogeneous opticospinal presentations.

A 13-year-old girl with proximal weakness and hypertrophic cardiomyopathy with Danon disease.

Danon disease is caused by deficiency of lysosome-associated membrane protein-2 (LAMP-2). It is characterized clinically by cardiomyopathy, myopathy, and mental retardation in boys. Herein we report a 13-year-old female patient with Danon disease who presented with early-onset skeletal myopathy and cardiomyopathy. She had a de novo novel mutation in the LAMP2 gene, and her muscles showed many autophagic vacuoles with sarcolemmal features and complete absence of LAMP-2 expression. To the best of our knowledge, this girl is one of the earliest-onset manifesting carriers of Danon disease with typical muscle pathology.

Clinical and imaging findings of systemic hyalinosis: two cases presenting with congenital arthrogryposis.

Systemic hyalinosis is a rare, multisystem, progressive, autosomal recessive disorder of connective tissue characterized by diffuse hyaline deposition in the skin, bone or viscera. Owing to its rarity and initial manifestations that resemble arthrogryposis congenital multiplexa, correct diagnosis can be elusive and often delayed. We present the computed tomography (CT) and whole-body (WB) magnetic resonance (MR) findings in two unrelated children with systemic hyalinosis who came to medical attention because of multiple joint contractures and limitation of motion in early infancy.

Glutaric aciduria type 1 in Korea: report of two novel mutations.

Glutaric aciduria type I (GA I) is an autosomal recessive disorder caused by a deficiency of glutaryl-CoA dehydrogenase. Although over 400 patients confirmed as GA I have been reported, reports from the Asian population had contributed to the minor proportion. We recently diagnosed two cases of GA I confirmed with mutational analysis. Here, we present their rather atypical clinical presentations with genetic characteristics for the first time in Korea. Profound developmental delay from birth, association of hearing loss, and neurological improvement after surgical intervention, were considered to be different clinical features from most reported cases. One patient was a compound heterozygote for p.Ser139Leu and p.Asp220Tyr, and the other for p.Ser139Leu and Glu160X. The mutations of the two alleles (p.Asp220Tyr and p.Glu160X) were novel and reports of p.Ser139Leu were rare both in Western and other Asian populations. These might suggest different genetic spectrum of Korean GA I patients.

Biochemical and genetic analysis of Leigh syndrome patients in Korea.

Sixteen Korean patients with Leigh syndrome were identified at the Seoul National University Children's Hospital in 2001-2006. Biochemical or molecular defects were identified in 14 patients (87.5%). Thirteen patients had respiratory chain enzyme defects; 9 had complex I deficiency, and 4 had combined defects of complex I+III+IV. Based on the biochemical defects, targeted genetic studies in 4 patients with complex I deficiency revealed two heteroplasmic mitochondrial DNA mutations in ND genes. One patient had the mitochondrial DNA T8993G point mutation. No mitochondrial DNA defects were identified in 11 (68.7%) of our LS patients, who probably have mutations in nuclear DNA. Although a limited study based in a single tertiary medical center, our findings suggest that isolated complex I deficiency may be the most common cause of Leigh syndrome in Korea.

Mutational analysis of TSC1 and TSC2 in Korean patients with tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by a broad phenotypic spectrum that includes seizures, mental retardation, renal dysfunction and dermatological abnormalities. TSC is caused by mutations affecting either of the tumor-suppressor genes TSC1 and TSC2. At least 495 mutations of TSC1 and TSC2 have been reported. Twenty-two males and 22 females who were diagnosed with TSC at the Seoul National University Children's Hospital between 1982 and 2002 were enrolled in the study. Forty-four patients were from different families and included nine familial cases and 35 sporadic cases. Denaturing high performance liquid chromatography and DNA sequencing analysis of TSC1 and TSC2 revealed 13 types of mutations (30%). One novel mutation of TSC1 and nine novel mutations of TSC2 were identified. The TSC1 mutation and one of the nine TSC2 mutations were missense mutations and seven of the nine TSC2 mutations caused truncation of proteins. One novel single nucleotide substitution was identified at the consensus splicing donor site of exon 39 (c.5,069-1G>A). This mutation is predicted to cause a splicing error. Of the TSC2 mutation loci, the correlation with cardiac rhabdomyoma was more significant when the mutation was in the C-terminal part of tuberin than the N-terminal part. This is the first extensive mutational analysis of TSC1 and TSC2 in Korean TSC patients.

Painful legs and moving toes syndrome in a 16-year-old girl.

Painful legs and moving toes (PLMT) syndrome is characterized by spontaneous movements of the digits and pain in one or both lower extremities. Of the reported cases, a majority of the patients was female, and the mean age of onset was 58 years. Only one pediatric case has been reported so far. Herein, we report the first adolescent case of PLMT in Korea. A 16-year-old girl complained of tingling pain in the left leg and involuntary movement of the ipsilateral great toe one month after a second untethering surgery. Three years ago, she had undergone untethering surgery to correct lipomeningomyelocele at the S2 level of the conus medullaris. At that time, she was diagnosed with polyradiculopathy at the left L5 level with axonal involvement. We diagnosed her with PLMT syndrome and prescribed gabapentin. Her symptoms diminished within a day. Complete relief from involuntary movement of the toe was achieved within four months. PLMT is a rare syndrome but it should be considered in the differential diagnosis of children and adolescents with limb pain and spontaneous movement in their toes.