Byung Chan Lim

Utility of next generation sequencing in genetic diagnosis of early onset neuromuscular disorders

Background Neuromuscular disorders are a clinically, pathologically, and genetically heterogeneous group. Even for the experienced clinician, an accurate diagnosis is often challenging due to the complexity of these disorders. Here, we investigated the utility of next generation sequencing (NGS) in early diagnostic algorithms to improve the diagnosis for patients currently lacking precise molecular characterisation, particularly for hereditary myopathies. Methods 43 patients presenting with early onset neuromuscular disorders from unknown genetic origin were tested by NGS for 579 nuclear genes associated with myopathy. Results In 21 of the 43 patients, we identified the definite genetic causes (48.8%). Additionally, likely pathogenic variants were identified in seven cases and variants of uncertain significance (VUS) were suspected in four cases. In total, 19 novel and 15 known pathogenic variants in 17 genes were identified in 32 patients. Collagen VI related myopathy was the most prevalent type in our cohort. The utility of NGS was highlighted in three cases with congenital myasthenia syndrome, as early diagnosis is important for effective treatment. Conclusions A targeted NGS can offer cost effective, safe and fairly rapid turnaround time, which can improve quality of care for patients with early onset myopathies and muscular dystrophies; in particular, collagen VI related myopathy and congenital myasthenia syndromes. Nevertheless, a substantial number of patients remained without molecular diagnosis in our cohort. This may be due to the intrinsic limitation of detection for some types of mutations by NGS or to the fact that other causative genes for neuromuscular disorders are yet to be identified.

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.

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.

Clinical and EEG risk factors for subsequent epilepsy in patients with complex febrile seizures

PURPOSE To identify the risk factors for subsequent epilepsy in patients with complex febrile seizures from a single-center retrospective cohort. METHODS The medical records of 1091 patients discharged with a diagnosis of febrile seizures from the Seoul National University Bundang Hospital from February 2004 to October 2009 were reviewed. One hundred eighty-three patients (107 boys and 76 girls) with complex febrile seizures who showed normal neurocognitive development were included in the analysis. Clinical characteristics, including features of complex febrile seizure, initial interictal electroencephalographic findings, and subsequent epilepsy, were reviewed and the odds ratio of subsequent epilepsy was estimated. The mean follow-up duration for subsequent epilepsy was 6.1 years (range, 2.5-8.0 years). RESULTS Complex febrile seizures were observed in 22.6% of all patients with febrile seizures. Among 183 patients with complex febrile seizures, 22 patients (12.0%) developed subsequent epilepsy. Prolonged (>10 min) seizure (p=0.031; odds ratio, 3.04; 95% confidence interval, 1.11-8.32) or the presence of multiple seizures for 24 h (p=0.032; odds ratio, 3.63; 95% confidence interval, 1.12-11.8) was significantly more frequent in patients with subsequent epilepsy, whereas the presence of focal seizure was not significantly different. Epileptiform discharges (focal in all cases) were significantly more frequent in patients with subsequent epilepsy (50% vs. 13%, p=0.002), with an odds ratio of 5.15 (95% confidence interval, 1.84-14.5). CONCLUSION The presence of epileptiform discharges is a significant risk factor for subsequent epilepsy in patients with complex febrile seizures. Electroencephalography should be considered in all patients with complex febrile seizures especially those who had multiple or prolonged seizures.

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 Childrens 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.

Long-term effectiveness of ethosuximide, valproic acid, and lamotrigine in childhood absence epilepsy

PURPOSE We performed this study to evaluate the long-term efficacy and tolerability of ethosuximide (ESX), valproic acid (VPA), and lamotrigine (LTG) as initial monotherapies for patients with newly diagnosed childhood absence epilepsy. METHODS We retrospectively reviewed the medical records of 128 patients (45 boys and 83 girls) diagnosed with childhood absence epilepsy at the Seoul National University Hospital. The diagnosis was based on the criteria proposed by Panayiotopoulos in 2005. We measured the seizure-free rate and the retention rate observed during 2 years of treatment. Follow-up electroencephalography (EEG), any reported adverse events, and reasons for antiepileptic drug (AED) discontinuation were reviewed. RESULTS The seizure-free rate of ESX (84%) was significantly higher than that of VPA (62%) and LTG (53%) at 3 months. The seizure-free rate of ESX (90%) was significantly higher than that of LTG (63%) at 6 months. After 9 months, there was no significant difference in seizure-free rate among the three groups. There were no significant differences among the three groups in terms of normalization of EEG at 12 months (ESX, 77%; VPA, 83%; and LTG, 64%), retention rate throughout the whole treatment period, and adverse-event rates (ESX, 25%; VPA, 29%; and LTG, 14%). CONCLUSION This study suggests that ESX, VPA, and LTG are equally effective in the long-term treatment of newly diagnosed CAE patients. However, the onset of efficacy was faster for ESX compared with VPA or LTG. Efficacy, tolerability, and adverse event profiles should be carefully considered when selecting AEDs to treat individual patients with CAE.

De Novo Interstitial Deletion of 3q22.3-q25.2 Encompassing FOXL2, ATR, ZIC1, and ZIC4 in a Patient With Blepharophimosis/Ptosis/Epicanthus Inversus Syndrome, Dandy-Walker Malformation, and Global Developmental Delay

We report a case carrying a de novo interstitial deletion of chromosome 3q22-q25. The clinical phenotype of this case included blepharophimosis/ptosis/epicanthus inversus syndrome, Dandy-Walker malformation, and global developmental delay. Contiguous heterozygous deletion of FOXL2, ATR, ZIC1, and ZIC4 was postulated as the causative mechanism of the clinical phenotype. The association of blepharophimosis, ptosis, and epicanthus inversus syndrome with developmental delay or mental retardation may be an indication for the use of brain imaging and chromosomal analysis capable of detecting chromosomal rearrangements encompassing several candidate genes.

GM3 synthase deficiency due to ST3GAL5 variants in two Korean female siblings: Masquerading as Rett syndrome-like phenotype.

There have been a few reports of GM3 synthase deficiency since the disease of the ganglioside biosynthetic pathway was first reported in 2004. It is characterized by infantile‐onset epilepsy with severe intellectual disability, blindness, cutaneous dyspigmentation, and choreoathetosis. Here we report the cases of two Korean female siblings with ST3GAL5 variants, who presented with a Rett‐like phenotype. They had delayed speech, hand stereotypies with a loss of purposeful hand movements, and choreoathetosis, but no clinical seizures. One of them had microcephaly, while the other had small head circumference less than 10th centile. There were no abnormal laboratory findings with the exception of a high lactate level. MECP2/CDKL5/FOXG1 genetic tests with an array comparative genomic hybridization revealed no molecular defects. Through whole‐exome sequencing of the proband, we found compound heterozygous ST3GAL5 variants (p.Gly201Arg and p.Cys195Ser), both of which were novel. The siblings were the same compound heterozygotes and their unaffected parents were heterozygous carriers of each variant. Liquid chromatography–mass spectrometry analysis confirmed a low level of GM3 and its downstream metabolites, indicating GM3 synthase deficiency. These cases expanded the clinical and genetic spectrum of the ultra‐rare disease, GM3 synthase deficiency with ST3GAL5 variants.

A case of Rubinstein-Taybi Syndrome with a CREB- binding protein gene mutation

Rubinstein-Taybi syndrome (RTS) is a congenital disorder characterized by typical facial features, broad thumbs and toes, with mental retardation. Additionally, tumors, keloids and various congenital anomalies including congenital heart defects have been reported in RTS patients. In about 50% of the patients, mutations in the CREB binding protein (CREBBP) have been found, which are understood to be associated with cell growth and proliferation. Here, we describe a typical RTS patient with Arnold-Chiari malformation. A mutation in the CREBBP gene, c.4944_4945insC, was identified by mutational analysis.

Cerebellum Can Be a Possible Generator of Progressive Myoclonus

A 19-month-old girl presented with progressive myoclonic jerking of both proximal lower extremities. On her brain magnetic resonance imaging (MRI), the authors found an ill-defined mass involving cerebellar vermis and the right middle cerebellar peduncle. 11C-methionine positron emission tomography (PET) showed no abnormalities, but 18F-fluorodeoxyglucose (18F-FDG) PET revealed a well-defined hypermetabolic focus. Depth electrodes were inserted deep into the mass, which recorded focal slow waves associated with the clinical myoclonus. Following the removal of the tumor, the myoclonus was completely resolved with no neurological deficit. Here, the authors present a case showing progressive myoclonus associated with a cerebellar ganglioglioma with the electrophysiological data, which provides strong supportive evidence that the cerebellum can be a myoclonus generator.