Expanding the Spectrum of Stress-Induced Childhood-Onset Neurodegeneration with Variable Ataxia and Seizures (CONDSIAS).

Stress-induced childhood-onset neurodegeneration with variable ataxia and seizures (CONDSIAS) is an extremely rare, autosomal recessive neurodegenerative disorder. It is caused by biallelic pathogenic variants in the ADPRS gene, which encodes an enzyme involved in DNA repair, and is characterized by exacerbations in relation to physical or emotional stress, and febrile illness. We report a 24-year-old female, who was compound heterozygous for two novel pathogenic variants revealed by whole exome sequencing. Additionally, we summarize the published cases of CONDSIAS. In our patient, onset of symptoms occurred at 5 years of age and consisted of episodes of truncal dystonic posturing, followed half a year later by sudden diplopia, dizziness, ataxia, and gait instability. Progressive hearing loss, urinary urgency, and thoracic kyphoscoliosis ensued. Present neurological examination revealed dysarthria, facial mini-myoclonus, muscle weakness and atrophy of hands and feet, leg spasticity with clonus, truncal and appendicular ataxia, and spastic-ataxic gait. Hybrid [18F]-fluorodeoxyglucose (FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) of the brain revealed cerebellar atrophy, particularly of the vermis, with corresponding hypometabolism. MRI of the spinal cord showed mild atrophy. After informed consent from the patient, we initiated experimental, off-label treatment with minocycline, a poly-ADP-polymerase (PARP) inhibitor, which has shown beneficial effects in a Drosophila fly model. The present case report expands the list of known pathogenic variants in CONDIAS and presents details of the clinical phenotype. Future studies will reveal whether PARP inhibition is an effective treatment strategy for CONDIAS.

Novel Homozygous Truncating Variant Widens the Spectrum of Early-Onset Multisystemic SYNE1 Ataxia.

Pathogenic variants in the SYNE1 gene are associated with a phenotypic spectrum spanning from late-onset, slowly progressive, relatively pure ataxia to early-onset, fast progressive multisystemic disease. Since its first description in 2007 as an adult-onset ataxia in French Canadian families, subsequent identification of patients worldwide has widened the clinical spectrum and increased the number of identified pathogenic variants. We report a 20-year-old Faroese female with early-onset progressive gait problems, weakness, dysphagia, slurred speech, orthostatic dizziness, and urge incontinence. Neurological examination revealed mild cognitive deficits, dysarthria, broken slow pursuit, hypometric saccades, weakness with spasticity, hyperreflexia, absent ankle reflexes, ataxia, and wide-based, spastic gait. Magnetic resonance imaging displayed atrophy of the cerebellum, brainstem, and spinal cord. Severely prolonged central motor conduction time and lower motor neuron involvement was demonstrated electrophysiologically. Fluorodeoxyglucose-positron emission tomography (FDG-PET) scan showed hypometabolism of the cerebellum and right frontal lobe. Muscle biopsy revealed chronic neurogenic changes and near-absent immunostaining for Nesprin-1. Next-generation sequencing revealed a previously undescribed homozygous truncating, likely pathogenic variant in the SYNE1 gene. The patient's mother and paternal grandfather were heterozygous carriers of the variant. Her father's genotype was unobtainable. We expand the list of likely pathogenic variants in SYNE1 ataxia with a novel homozygous truncating variant with proximity to the C-terminus and relate it to a phenotype comprising early-onset cerebellar deficits, upper and lower motor neuron involvement and cognitive deficits. Also, we report novel findings of focally reduced frontal lobe FDG-PET uptake and motor evoked potential abnormalities suggestive of central demyelination.

Peripheral helper T cells in the pathogenesis of multiple sclerosis.

BACKGROUND: Peripheral helper T cells (Tph) are likely implicated in the pathogenesis of various inflammatory diseases. Tph cells share functions with follicular helper T cells, including plasma cell differentiation and antibody production. OBJECTIVE AND METHODS: To investigate a possible role of Tph cells in the pathogenesis of multiple sclerosis (MS), we used flow cytometry to analyze the function, phenotype, and central nervous system (CNS)-recruitment of Tph cells in the blood and cerebrospinal fluid (CSF) from controls and patients with relapsing-remitting (RR) and primary progressive (PP) MS. RESULT: This study identified two functionally distinct Tph cell populations and a regulatory counterpart, Tpr cells. No differences in blood frequencies, cytokine production, or potential to interact with B cells were found between controls and patients with MS. Along with an equal CNS-migration potential, we found both Tph cell populations enriched in the CSF; and surprisingly, an increased frequency of intrathecal Tph cells in the control group compared to patients with MS. CONCLUSION: Altogether, we did not find an increased frequency of CSF Tph cells in patients with RRMS or PPMS. Our findings indicate that rather than being involved in MS pathogenesis, Tph cells may be implicated in normal CNS immunosurveillance.

Enhancement of Autophagy and Solubilization of Ataxin-2 Alleviate Apoptosis in Spinocerebellar Ataxia Type 2 Patient Cells.

Spinocerebellar ataxia type 2 (SCA2), a rare polyglutamine neurodegenerative disorder caused by a CAG repeat expansion in the ataxin-2 gene, exhibits common cellular phenotypes with other neurodegenerative disorders, including oxidative stress and mitochondrial dysfunction. Here, we show that SCA2 patient cells exhibit higher levels of caspase-8- and caspase-9-mediated apoptotic activation than control cells, cellular phenotypes that we find to be exacerbated by reactive oxygen species (ROS) and inhibition of autophagy. We also suggest that oligomerization of mutant ataxin-2 protein is likely to be the cause of the observed cellular phenotypes by causing inhibition of autophagy and by inducing ROS generation. Finally, we show that removal of ataxin-2 oligomers, either by increasing autophagic clearance or by oligomer dissolution, appears to alleviate the cellular phenotypes. Our results suggest that oligomerized ataxin-2 and oxidative stress affect autophagic clearance in SCA2 cells, contributing to the pathophysiology, and that activation of autophagy or clearance of oligomers may prove to be effective therapeutic strategies.

Serum Neurofilament Light in Patients with Frontotemporal Dementia Caused by CHMP2B Mutation.

INTRODUCTION: The potential of neurofilament light (NfL) as a blood-based biomarker is currently being investigated in autosomal dominant neurodegenerative disease. This study explores the clinical utility of serum-NfL in frontotemporal dementia due to CHMP2B mutation (FTD-3). METHODS: This cross-sectional study included serum and CSF data from 38 members of the Danish FTD-3 family: 12 affected CHMP2B mutation carriers, 10 presymptomatic carriers, and 16 noncarriers. Serum-NfL levels measured by single-molecule array (Simoa) technology were tested for associations with the clinical groups and clinical parameters. Serum and CSF data were compared, and CSF/serum-albumin ratio was included as a measure of blood-brain barrier (BBB) function. RESULTS: Serum-NfL concentrations were significantly increased in symptomatic CHMP2B mutation carriers compared to presymptomatic carriers and in both groups compared to healthy family controls. Serum-NfL levels appear to increase progressively with age in presymptomatic carriers, and this is perhaps followed by a change in trajectory when patients become symptomatic. Measurements of NfL in serum and CSF were highly correlated and fold-changes in serum and CSF between clinical groups were similar. Increase in serum-NFL levels was correlated with reduced ACE-score. Higher CSF/serum-albumin ratios were demonstrated in FTD-3 patients, but this did not affect the significant associations between serum-NfL and clinical groups. CONCLUSION: Serum-NfL could be utilized as an accurate surrogate marker of CSF levels to segregate symptomatic CHMP2B carriers, presymptomatic carriers, and non-carriers. The observed indication of BBB dysfunction in FTD-3 patients did not confound this use of serum-NfL. The results support the occurrence of mutation-related differences in NfL dynamics in familial FTD.

Quantitative Measurements of Motor Function in Alzheimer's Disease, Frontotemporal Dementia, and Dementia with Lewy Bodies: A Proof-of-Concept Study.

BACKGROUND: This study examines the efficacy of using quantitative measurements of motor dysfunction, compared to clinical ratings, in Alzheimer's disease (AD), frontotemporal dementia (FTD), and dementia with Lewy bodies (DLB). METHODS: In this cross-sectional study, 49 patients with a diagnosis of AD (n = 17), FTD (n = 19), or DLB (n = 13) were included and underwent cognitive testing, clinical motor evaluation, and quantitative motor tests: pronation/supination hand tapping, grasping and lifting, and finger and foot tapping. RESULTS: Our results revealed significantly higher Q-Motor values in pronation/supination and in grip lift force assessment in AD, FTD, and DLB compared to healthy controls (HC). Q-Motor values detected significant differences between AD and HC, while clinical ratings did not. CONCLUSION: Our results suggest that quantitative measurements provide more objective and sensitive measurements of motor dysfunction in dementia.

SCA28: Novel Mutation in the AFG3L2 Proteolytic Domain Causes a Mild Cerebellar Syndrome with Selective Type-1 Muscle Fiber Atrophy.

The spinocerebellar ataxias (SCA) are a group of rare inherited neurodegenerative diseases characterized by slowly progressive cerebellar ataxia, resulting in unsteady gait, clumsiness, and dysarthria. The disorders are predominantly inherited in an autosomal dominant manner. Mutations in the gene AFG3L2 that encodes a subunit of the mitochondrial m-AAA protease have previously been shown to cause spinocerebellar ataxia type 28 (SCA28). Here, we present the clinical phenotypes of three patients from a family with autosomal dominant cerebellar ataxia and show by molecular genetics and in silico modelling that this is caused by a novel missense mutation in the AFG3L2 gene. Furthermore, we show, for the first time, fluorodeoxyglucose-positron emission tomography (FDG-PET) scans of the brain and selective type I fiber atrophy of skeletal muscle of SCA28 patients indicating non-nervous-system involvement in SCA28 as well.

A Novel TTBK2 De Novo Mutation in a Danish Family with Early-Onset Spinocerebellar Ataxia.

Spinocerebellar ataxia type 11 (SCA11) is rare and has previously been described in four families worldwide. We report a Danish family with onset of symptoms in early childhood and affected family members in two generations. The proband, a Danish female born in 1968, and family members were examined. Exome sequencing was performed and a "movement disorders" gene panel consisting of approximately 200 genes was used for filtering, while Sanger sequencing was used for subsequent testing for the mutation in the family. Onset of symptoms in affected family members was in early childhood. A novel frameshift mutation (c.1205_1207delinsA) in the tau-tubulin kinase 2 encoding gene, TTBK2, was identified, which was compatible with a diagnosis of SCA11. The mutation was subsequently identified in her two affected sons but not in the unaffected parents or her unaffected brother. This report further delineates the phenotypic spectrum of the rare SCA11 disease. In contrast to previously reported cases, onset of symptoms was in early childhood and the mutation was de novo in the proband.

Defining active progressive multiple sclerosis.

BACKGROUND: It is unknown whether disease activity according to consensus criteria (magnetic resonance imaging activity or clinical relapses) associate with cerebrospinal fluid (CSF) changes in progressive multiple sclerosis (MS). OBJECTIVE: To compare CSF biomarkers in active and inactive progressive MS according to consensus criteria. METHODS: Neurofilament light chain (NFL), myelin basic protein (MBP), IgG-index, chitinase-3-like-1 (CHI3L1), matrix metalloproteinase-9 (MMP-9), chemokine CXCL13, terminal complement complex, leukocyte counts and nitric oxide metabolites were measured in primary ( n = 26) and secondary progressive MS ( n = 26) and healthy controls ( n = 24). RESULTS: Progressive MS patients had higher CSF cell counts, IgG-index, CHI3L1, MMP-9, CXCL13, NFL and MBP concentrations. Active patients were younger and had higher NFL, CXCL13 and MMP-9 concentrations than inactive patients. Patients with active disease according to consensus criteria or detectable CXCL13 or MMP-9 in CSF were defined as having combined active progressive MS. These patients had increased CSF cell counts, IgG-index and MBP, NFL and CHI3L1 concentrations. Combined inactive patients only had increased IgG-index and MBP concentrations. CONCLUSION: Patients with combined active progressive MS show evidence of inflammation, demyelination and neuronal/axonal damage, whereas the remaining patients mainly show evidence of active demyelination. This challenges the idea that neurodegeneration independent of inflammation is crucial in disease progression.

Personality traits in Huntington's disease: An exploratory study of gene expansion carriers and non-carriers.

Huntington's disease (HD) is associated with risk for developing psychiatric symptoms. Vulnerability or resilience to psychiatric symptoms may be associated with personality traits. This exploratory study, aimed to investigate personality traits in a large cohort of HD carriers and at risk gene-expansion negative individuals (HD non-carriers), exploring whether carrying the HD gene or growing up in an HD family influences personality traits. Forty-seven HD carriers, Thirty-nine HD non-carriers, and 121 healthy controls answered the Danish version of the revised NEO personality inventory. Comparisons between HD carriers and HD non-carriers were mostly non-significant but the combined group of HD carriers and non-carriers showed significantly higher scores on the facets: "hostility," "assertiveness," and "activity" and on the trait "Conscientiousness" relative to controls, "Conscientiousness" have been associated with resilience to psychiatric symptoms. Twelve HD carriers and non-carriers were classified as depressed and showed significantly lower scores on "Extraversion" and "Conscientiousness" and significantly higher scores on "Neuroticism," which are associated with vulnerability to psychiatric symptoms. Our findings suggest that, there is no direct effect of the HD gene on personality traits, but that personality assessment may be relevant to use when identifying individuals from HD families who are vulnerable to develop psychiatric symptoms. © 2016 Wiley Periodicals, Inc.

Cerebrospinal Fluid Biomarkers in Familial Forms of Alzheimer's Disease and Frontotemporal Dementia.

As dementia is a fast-growing health care problem, it is becoming an increasingly urgent need to provide an early diagnosis in order to offer patients the best medical treatment and care. Validated biomarkers which reflect the pathology and disease progression are essential for diagnosis and are important when developing new therapies. Today, the core protein biomarkers amyloid-ß42, total tau and phosphorylated tau in the cerebrospinal fluid (CSF) are used to diagnose Alzheimer's disease (AD), because these biomarkers have shown to reflect the underlying amyloid and tau pathology. However, the biomarkers have proved insufficient predictors of dementias with a different pathology, e.g. frontotemporal dementia (FTD); furthermore, the biomarkers are not useful for early AD diagnosis. Familial dementias with a known disease-causing mutation can be extremely valuable to study; yet the biomarker profiles in patients with familial dementias are not clear. This review summarizes CSF biomarker findings from studies on symptomatic and presymptomatic individuals carrying a mutation in one of the genes known to cause early-onset familial AD or FTD. In conclusion, the biomarker profile of inherited AD is quite similar between carriers of different mutations as well as similar to the profile found in sporadic AD, whereas familial FTD does not seem to have a clear biomarker profile. Hence, new biomarkers are needed for FTD.

Assessing impairment of executive function and psychomotor speed in premanifest and manifest Huntington's disease gene-expansion carriers.

Executive functions (EF) and psychomotor speed (PMS) has been widely studied in Huntington's disease (HD). Most studies have focused on finding markers of disease progression by comparing group means at different disease stages. Our aim was to investigate performances on nine measures of EF and PMS in a group of premanifest and manifest HD-gene expansion carriers and to investigate which measures were most sensitive for assessment of individual patients by analyzing frequencies of impaired performances relative to healthy controls. We recruited HD gene-expansion carriers, 48 manifest and 50 premanifest and as controls 39 healthy gene-expansion negative individuals. All participants underwent neurological examination and neuropsychological testing with nine cognitive measures. The frequency of impairment was investigated using cutoff scores. In group comparisons the manifest HD gene-expansion carriers scored significantly worse than controls on all tests and in classification of individual scores the majority of scores were classified as probably impaired (10th percentile) or impaired (5th percentile) with Symbol Digit Modalities Test (SDMT) being the most frequently impaired. Group comparisons of premanifest HD gene-expansion carriers and healthy controls showed significant differences on SDMT and Alternating fluency tests. Nevertheless the frequencies of probably impaired and impaired scores on individual tests were markedly higher for Alternating and Lexical fluency tests than for SDMT. We found distinct group differences in frequency of impairment on measures of EF and PMS in manifest and premanifest HD gene-expansion carriers. Our results indicate to what degree these measures can be expected to be clinically impaired.

Endo-lysosomal protein concentrations in CSF from patients with frontotemporal dementia caused by CHMP2B mutation.

Introduction: Increasing evidence implicates proteostatic dysfunction as an early event in the development of frontotemporal dementia (FTD). This study aimed to explore potential cerebrospinal fluid (CSF) biomarkers associated with the proteolytic systems in genetic FTD caused by CHMP2B mutation. Methods: Combining solid-phase extraction and parallel reaction monitoring mass spectrometry, a panel of 47 peptides derived from 20 proteins was analyzed in CSF from 31 members of the Danish CHMP2B-FTD family. Results: Compared with family controls, mutation carriers had significantly higher levels of complement C9, lysozyme and transcobalamin II, and lower levels of ubiquitin, cathepsin B, and amyloid precursor protein. Discussion: Lower CSF ubiquitin concentrations in CHMP2B mutation carriers indicate that ubiquitin levels relate to the specific disease pathology, rather than all-cause neurodegeneration. Increased lysozyme and complement proteins may indicate innate immune activation. Altered levels of amyloid precursor protein and cathepsins have previously been associated with impaired lysosomal proteolysis in FTD. Highlights: CSF markers of proteostasis were explored in CHMP2B-mediated frontotemporal dementia (FTD).31 members of the Danish CHMP2B-FTD family were included.We used solid-phase extraction and parallel reaction monitoring mass spectrometry.Six protein levels were significantly altered in CHMP2B-FTD compared with controls.Lower CSF ubiquitin levels in patients suggest association with disease mechanisms.

Golgi fragmentation - One of the earliest organelle phenotypes in Alzheimer's disease neurons.

Alzheimer's disease (AD) is the most common cause of dementia, with no current cure. Consequently, alternative approaches focusing on early pathological events in specific neuronal populations, besides targeting the well-studied amyloid beta (Aß) accumulations and Tau tangles, are needed. In this study, we have investigated disease phenotypes specific to glutamatergic forebrain neurons and mapped the timeline of their occurrence, by implementing familial and sporadic human induced pluripotent stem cell models as well as the 5xFAD mouse model. We recapitulated characteristic late AD phenotypes, such as increased Aß secretion and Tau hyperphosphorylation, as well as previously well documented mitochondrial and synaptic deficits. Intriguingly, we identified Golgi fragmentation as one of the earliest AD phenotypes, indicating potential impairments in protein processing and post-translational modifications. Computational analysis of RNA sequencing data revealed differentially expressed genes involved in glycosylation and glycan patterns, whilst total glycan profiling revealed minor glycosylation differences. This indicates general robustness of glycosylation besides the observed fragmented morphology. Importantly, we identified that genetic variants in Sortilin-related receptor 1 (SORL1) associated with AD could aggravate the Golgi fragmentation and subsequent glycosylation changes. In summary, we identified Golgi fragmentation as one of the earliest disease phenotypes in AD neurons in various in vivo and in vitro complementary disease models, which can be exacerbated via additional risk variants in SORL1.

Intravenous immunoglobulin treatment in a patient with adrenomyeloneuropathy.

BACKGROUND: Adrenomyeloneuropathy (AMN) is one of several phenotypes of the adrenoleukodystrophy spectrum caused by mutations in the ABCD1 gene on the X chromosome. An inflammatory component is part of the disease complex ranging from severe childhood CNS demyelination to spinal cord and peripheral nerve degeneration. CASE PRESENTATION: We present a patient with clinical progressive AMN and severe lower limb pain. Longitudinal brain magnetic resonance spectroscopy showed a constant slightly elevated myoinositol/total creatine ratio during the five year treatment period, probably reflecting demyelination, microglial activation and gliosis, indicating an inflammatory response. The pain was refractory to conventional therapy but intravenous immunoglobulin (IVIG) treatment was highly efficient. CONCLUSION: IVIG may be considered as a last resort for treatment of refractory pain in AMN patients with indications of an inflammatory component.

Widening the spectrum of spinocerebellar ataxia autosomal recessive type 10 (SCAR10).

Biallelic pathogenic variants in the ANO10 gene cause spinocerebellar ataxia recessive type 10. We report two patients, both compound heterozygous for ANO10 variants, including two novel variants. Both patients had onset of cerebellar ataxia in adulthood with slow progression and presented corticospinal tract signs, eye movement abnormalities and cognitive executive impairment. One of them had temporal lobe epilepsy and she also carried a heterozygous variant in CACNB4, a potential risk gene for epilepsy. Both patients had pronounced cerebellar atrophy on cerebral magnetic resonance imaging (MRI) and reduced metabolic activity in cerebellum as well as in the frontal lobes on 2-deoxy-2-(18F)fluoro-D-glucose positron emission tomography ((18F)FDG PET) scans. We provide comprehensive clinical, radiological and genetic data on two patients carrying likely pathogenic ANO10 gene variants. Furthermore, we provide evidence for a cerebellar as well as a frontal involvement on brain (18F)FDG PET scans which has not previously been reported.

Episodic ataxia type 2 (EA2) with interictal myokymia and focal dystonia.

Episodic ataxia type 1 and 2 (EA1 and EA2) are the most well-described of the episodic ataxias. They are autosomal dominantly inherited early-onset diseases characterized by attacks of cerebellar dysfunction. EA1 is clinically characterized by short episodes of ataxia with interictal myokymia, whereas EA2 is characterized by longer-lasting recurrent ataxia, slurred speech, and interictal nystagmus. We report on a patient with EA2 with interictal focal dystonia and also interictal myokymia, which is hitherto not reported as an interictal feature associated to EA2. The patient carries a previously described heterozygous pathogenic de novo frameshift variant in the CACNA1A gene, establishing the diagnosis of EA2. She had symptom onset at age 13 and from age 48 she developed interictal myokymia and focal dystonia as illustrated in Supplemental Movie S1. We conclude that interictal myokymia and focal dystonia may be interictal features associated to EA2 caused by the cerebellar pathophysiology of EA2. Episodes of ataxia were successfully treated with acetazolamide in low dose, whereas the interictal features were unresponsive to acetazolamide.

Huntington's disease: effect of memantine on FDG-PET brain metabolism?

In this open-label pilot study, the authors evaluated the effect of memantine on the distribution of brain glucose metabolism in four Huntington's disease (HD) patients as determined by serial 18-fluoro-deoxyglucose [F(18)]FDG-PET scans over a period of 3-4 months (90-129 days, with one patient choosing to continue treatment over the 18-month follow-up period). The treatment regimen was well tolerated. No significant differences on neuropsychological parameters before and after treatment were detected; but the patient who continued treatment did not deteriorate at 18 months' reevaluation, whereas the three patients who had stopped treatment after 3 to 4 months had minor progression in all cognitive domains on re-evaluation 12 months after the end of treatment.

Cortical Frontoparietal Network Dysfunction in CHMP2B-Frontotemporal Dementia.

A rare cause of inherited frontotemporal dementia (FTD) is a mutation in the CHMP2B gene on chromosome 3 leading to the autosomal dominantly inherited FTD (CHMP2B-FTD). Since CHMP2B-FTD is clinically well-characterized, and patients show a distinct pattern of executive dysfunction, the condition offers possible insight in the early electroencephalographic (EEG) changes in the cortical networks. Specifically, EEG microstate analysis parses the EEG signals into topographies believed to represent discrete network activations. We investigated the EEG dynamics in patients with symptomatic CHMP2B-FTD (n = 5) as well as pre-symptomatic mutation carriers (n = 5) compared to non-carrier family members (n = 6). The data was parsed into four archetypal microstates and global power was calculated. A trend was found for lower occurrence in microstate D in CHMP2B-FTD (p-value = 0.177, F-value = 2.036). Patients with recent symptom onset (<1 year) showed an increased duration of microstate D, whereas patients who had been symptomatic for longer periods (>2 years) showed decreased duration. Patients with CHMP2B-FTD present with executive dysfunction, and microstate D has previously been shown to be associated with the fronto-parietal network. The biphasic pattern may represent the pathophysiological changes in brain dynamics during neurodegeneration, which may apply to other neurodegenerative diseases.

Novel mutations in EPM2A and NHLRC1 widen the spectrum of Lafora disease.

PURPOSE: Lafora disease (LD) is an autosomal recessive form of progressive myoclonus epilepsy with onset in childhood or adolescence and with fatal outcome caused by mutations in two genes: EPM2A and NHLRC1. The aim of this study was to characterize the mutation spectrum in a cohort of unrelated patients with presumed LD. METHODS: Sequencing of the two genes and search for large rearrangements was performed in 46 unrelated patients with suspected LD, 33 originating from France and the others from different countries. Patients were classified into two groups according to the clinical presentation. RESULTS: Mutations of various types were found in EPM2A in 10 patients and in NHLRC1 in 4 patients. Mutations were found in 14 (93%) of 15 patients with classical clinical and electroencephalography (EEG) presentation of LD and in no patients with an atypical presentation. Ten mutations were novel, including the first substitution reported in a donor splice site of EPM2A, leading to the deletion of exon 2 at the RNA level. Four large deletions, including two deletions of exon 2 with different sizes and breakpoints, were found in EPM2A, corresponding to 20% of the alleles of this gene. DISCUSSION: We described several novel mutations of EPM2A and NHLRC1 and brought additional data to the genetic epidemiology of LD. This study emphasized the high mutation rate in patients with classical LD as well as the high negativity rate of skin biopsy.