Association between acute complications in PMM2-CDG patients and haemostasis anomalies: Data from a multicentric study and suggestions for acute management.

OBJECTIVES: Patients with PMM2-CDG develop acute events (stroke-like episodes (SLEs), thromboses, haemorrhages, seizures, migraines) associated with both clotting factors (factor XI) and coagulation inhibitors (antithrombin, protein C and protein S) deficiencies. The aim of the study was to correlate acute events to haemostasis and propose practical guidelines. METHODS: In this multicentric retrospective study, we evaluated clinical, radiological, haemostasis and electroencephalography data for PMM2-CDG patients hospitalized for acute events. Cerebral events were classified as thrombosis, haemorrhage, SLE, or "stroke mimic" (SM: normal brain imaging or evoking a migraine). RESULTS: Thirteen patients had a total of 31 acute episodes: 27 cerebral events with 7 SLEs, 4 venous thromboses, 4 haemorrhages (3 associated with thrombosis), 15 SMs at a mean age of 7.7 years; 4 non-cerebral thromboses, one of which included bleeding. A trigger was frequently involved (infection, head trauma). Although sometimes normal at baseline state, factor XI, antithrombin and protein C levels decreased during these episodes. No correlation between haemostasis anomalies and type of acute event was found. DISCUSSION: Acute events in PMM2-CDG are not negligible and are associated with haemostasis anomalies. An emergency protocol is proposed for their prevention and treatment (https://www.filiere-g2m.fr/urgences). For cerebral events, brain Magnetic Resonance Imaging with perfusion weight imaging and diffusion sequences, electroencephalogram and haemostasis protein levels guide the treatment: anticoagulation, antithrombin or fresh frozen plasma supplementation, antiepileptic therapy. Preventing bleeding and thrombosis is required in cases of surgery, prolonged immobilization, hormone replacement therapy. CONCLUSION: Acute events in PMM2-CDG are associated with abnormal haemostasis, requiring practical guidance.

Treatment of new onset refractory status epilepticus/febrile infection-related epilepsy syndrome with tocilizumab in a child and a young adult.

New onset refractory status epilepticus (NORSE) is a rare and devastating condition occurring in a previously healthy patient. It is called febrile infection-related epilepsy syndrome (FIRES) when preceded by a febrile infection. It often leads to intensive care treatment, including antiseizure drugs in combination with anesthetic agents, and sometimes ketogenic diet. The mortality rate is high, and severe epileptic and neuropsychiatric sequelae are usually observed. Based on the possible role of neuroinflammation, intravenous immunoglobulin, corticosteroids, and immunomodulatory treatment (anti-IL1, IL6) can be added. We describe here a child and a young adult with FIRES, both treated with tocilizumab. We observed a rapid positive response on the status epilepticus and good tolerance, but different neurological outcomes for our two patients. Further prospective studies may be necessary both to confirm the efficacy and the safety of this promising treatment and to optimize the immunomodulatory strategy in FIRES/NORSE.

UQCRC2-related mitochondrial complex III deficiency, about 7 patients.

Isolated complex III defect is a relatively rare cause of mitochondrial disorder. New genes involved were identified in the last two decades, with only a few cases described for each deficiency. UQCRC2, which encodes ubiquinol-cytochrome c reductase core protein 2, is one of the eleven structural subunits of complex III. We report seven French patients with UQCRC2 deficiency to complete the phenotype reported so far. We highlight the similarities with neoglucogenesis defect during decompensations - hypoglycaemias, liver failure and lactic acidosis - and point out the rapid improvement with glucose fluid infusion, which is a remarkable feature for a mitochondrial disorder. Finally, we discuss the relevance of coenzyme Q10 supplementation in this defect.

Putative founder effect of Arg338* AP4M1 (SPG50) variant causing severe intellectual disability, epilepsy and spastic paraplegia: Report of three families.

Bi-allelic variants affecting one of the four genes encoding the AP4 subunits are responsible for the "AP4 deficiency syndrome." Core features include hypotonia that progresses to hypertonia and spastic paraplegia, intellectual disability, postnatal microcephaly, epilepsy, and neuroimaging features. Namely, AP4M1 (SPG50) is involved in autosomal recessive spastic paraplegia 50 (MIM#612936). We report on three patients with core features from three unrelated consanguineous families originating from the Middle East. Exome sequencing identified the same homozygous nonsense variant: NM_004722.4(AP4M1):c.1012C>T p.Arg338* (rs146262009). So far, four patients from three other families carrying this homozygous variant have been reported worldwide. We describe their phenotype and compare it to the phenotype of patients with other variants in AP4M1. We construct a shared single-nucleotide polymorphism (SNP) haplotype around AP4M1 in four families and suggest a probable founder effect of Arg338* AP4M1 variant with a common ancestor most likely of Turkish origin.

The different clinical facets of SYN1-related neurodevelopmental disorders.

Synapsin-I (SYN1) is a presynaptic phosphoprotein crucial for synaptogenesis and synaptic plasticity. Pathogenic SYN1 variants are associated with variable X-linked neurodevelopmental disorders mainly affecting males. In this study, we expand on the clinical and molecular spectrum of the SYN1-related neurodevelopmental disorders by describing 31 novel individuals harboring 22 different SYN1 variants. We analyzed newly identified as well as previously reported individuals in order to define the frequency of key features associated with these disorders. Specifically, behavioral disturbances such as autism spectrum disorder or attention deficit hyperactivity disorder are observed in 91% of the individuals, epilepsy in 82%, intellectual disability in 77%, and developmental delay in 70%. Seizure types mainly include tonic-clonic or focal seizures with impaired awareness. The presence of reflex seizures is one of the most representative clinical manifestations related to SYN1. In more than half of the cases, seizures are triggered by contact with water, but other triggers are also frequently reported, including rubbing with a towel, fever, toothbrushing, fingernail clipping, falling asleep, and watching others showering or bathing. We additionally describe hyperpnea, emotion, lighting, using a stroboscope, digestive troubles, and defecation as possible triggers in individuals with SYN1 variants. The molecular spectrum of SYN1 variants is broad and encompasses truncating variants (frameshift, nonsense, splicing and start-loss variants) as well as non-truncating variants (missense substitutions and in-frame duplications). Genotype-phenotype correlation revealed that epileptic phenotypes are enriched in individuals with truncating variants. Furthermore, we could show for the first time that individuals with early seizures onset tend to present with severe-to-profound intellectual disability, hence highlighting the existence of an association between early seizure onset and more severe impairment of cognitive functions. Altogether, we present a detailed clinical description of the largest series of individuals with SYN1 variants reported so far and provide the first genotype-phenotype correlations for this gene. A timely molecular diagnosis and genetic counseling are cardinal for appropriate patient management and treatment.

A homozygous MED11 C-terminal variant causes a lethal neurodegenerative disease.

PURPOSE: The mediator (MED) multisubunit-complex modulates the activity of the transcriptional machinery, and genetic defects in different MED subunits (17, 20, 27) have been implicated in neurologic diseases. In this study, we identified a recurrent homozygous variant in MED11 (c.325C>T; p.Arg109Ter) in 7 affected individuals from 5 unrelated families. METHODS: To investigate the genetic cause of the disease, exome or genome sequencing were performed in 5 unrelated families identified via different research networks and Matchmaker Exchange. Deep clinical and brain imaging evaluations were performed by clinical pediatric neurologists and neuroradiologists. The functional effect of the candidate variant on both MED11 RNA and protein was assessed using reverse transcriptase polymerase chain reaction and western blotting using fibroblast cell lines derived from 1 affected individual and controls and through computational approaches. Knockouts in zebrafish were generated using clustered regularly interspaced short palindromic repeats/Cas9. RESULTS: The disease was characterized by microcephaly, profound neurodevelopmental impairment, exaggerated startle response, myoclonic seizures, progressive widespread neurodegeneration, and premature death. Functional studies on patient-derived fibroblasts did not show a loss of protein function but rather disruption of the C-terminal of MED11, likely impairing binding to other MED subunits. A zebrafish knockout model recapitulates key clinical phenotypes. CONCLUSION: Loss of the C-terminal of MED subunit 11 may affect its binding efficiency to other MED subunits, thus implicating the MED-complex stability in brain development and neurodegeneration.

Intravenous administration of a branched-chain amino-acid-free solution in children and adults with acute decompensation of maple syrup urine disease: a prospective multicentre observational study.

BACKGROUND: Patients with maple syrup urine disease (MSUD) experiencing metabolic decompensations have traditionally been treated with branched-chain amino acid (BCAA)-free mixture via oral or nasogastric administration routes. In some patients, enteral administration is not possible, either because the patient presents with vomiting, coma, or refuses nasogastric administration, thus intravenous (IV) BCAA-free solution is an appropriate intervention for these challenging cases. AIMS: This study aimed to evaluate the effectiveness and safety of managing metabolic decompensations by administering an IV BCAA-free solution. METHODS: This is an observational prospective study of data from MSUD patients hospitalised for decompensation episodes between 2010 and 2016 at 6 centres for rare metabolic diseases in France. RESULTS: A total of 24 patients (16 males; 8 females) experiencing 126 MSUD metabolic decompensation episodes (39 in children; 87 in adults) were admitted to hospital. At presentation, mean leucine plasma concentration was ≥ 381 µmol/L in 113/126 (89.7%) episodes. Children were treated with continuous IV BCAA-free solution at doses of 0.8 to 2.0 g/kg/day, for 4.8 days and adults for 3.8 days at doses of 0.5 to 2.6 g/kg/day. In the efficacy set of 102 analysable episodes leucine concentrations were normalised (to below 381 µmol/L) in 82% (n = 18/22) of episodes in children and in 84% (n = 67/80) of episodes in adults. Mean time to leucine normalisation was 3.0 days. This was significantly (p < 0.001) shorter than the algorithmically predicted time to leucine normalisation with traditional BCAA-free mixture. Duration of hospitalisation was significantly longer for children than for adults (7.1 days in children vs 5.2 days in adults, p = 0.012). No treatment-related adverse events were reported in any patients on IV BCAA-free solution. CONCLUSION: The IV BCAA-free solution is safe and effective in normalising leucine concentrations during MSUD decompensation episodes in both children and adults, offering a practical treatment alternative for those patients who cannot receive BCAA-free mixture via oral or nasogastric routes.

The EPIGENE network: A French initiative to harmonize and improve the nationwide diagnosis of monogenic epilepsies.

BACKGROUND: The EPIGENE network was created in 2014 by four multidisciplinary teams composed of geneticists, pediatric neurologists and neurologists specialized in epileptology and neurophysiology. The ambition of the network was to harmonize and improve the diagnostic strategy of Mendelian epileptic disorders using next-generation sequencing, in France. Over the years, five additional centers have joined EPIGENE and the network has been working in close collaboration, since 2018, with the French reference center for rare epilepsies (CRéER). RESULTS: Since 2014, biannual meetings have led to the design of four successive versions of a monogenic epilepsy gene panel (PAGEM), increasing from 68 to 144 genes. A total of 4035 index cases with epileptic disorders have been analyzed with a diagnostic yield of 31% (n = 1265/4035). The top 10 genes, SCN1A, KCNQ2, STXBP1, SCN2A, SCN8A, PRRT2, PCDH19, KCNT1, SYNGAP1, and GRIN2A, account for one-sixth of patients and half of the diagnoses provided by the PAGEM. CONCLUSION: These results suggest that a gene-panel approach is an efficient first-tier test for the genetic diagnosis of Mendelian epileptic disorders. In a near future, French patients with "drug-resistant epilepsies with seizure-onset in the first two-years of life" can benefit from whole-genome sequencing (WGS), as a second line genetic screening with the implementation of the 2025 French Genomic Medicine Plan. The EPIGENE network has also promoted scientific collaborations on genetic epilepsies within CRéER.

Sebelipase alfa enzyme replacement therapy in Wolman disease: a nationwide cohort with up to ten years of follow-up.

BACKGROUND: Wolman disease (WD), the rapidly progressive phenotype of lysosomal acid lipase (LAL) deficiency, presents in neonates with failure to thrive and hepatosplenomegaly, and leads to multi-organ failure and death before 12 months of age. In clinical trials, enzyme replacement therapy (ERT) with sebelipase alfa led to improved survival, growth and biological parameters in WD patients followed up to 5 years. Long-term follow-up and health-related quality of life (HRQoL) evaluation are lacking. RESULTS: We performed a nationwide, retrospective study of sebelipase alfa in WD patients. Five patients with abolished LAL activity and bi-allelic LIPA mutations were included with a median follow-up of 7 years (1-10). ERT was initiated at a median age of 1 month (0-4). Infusion tolerance was excellent on the long-term with only one patient requiring systematic pre-medication. Cholestyramine, fat-soluble vitamin supplements and a specific diet (high in medium-chain triglycerides and low in long-chain fatty acids) were prescribed. Liver function tests, plasma lipid profiles, fat-soluble vitamin levels and growth parameters improved. Three patients transiently exhibited a neuromyopathic phenotype (footdrop gait, waddling walk or muscle fatigue) but electromyography and muscle strength testing were normal. At last follow-up, all patients were alive with normal growth parameters and a satisfactory HRQoL, no patient had special education needs, and one patient required parenteral nutrition since an acute gastroenteritis. CONCLUSIONS: Early ERT initiation allowed 100% survival with positive outcomes. Very long-term follow-up and hematopoietic stem cell transplantation while on ERT should be evaluated to strengthen the benefits of sebelipase alfa.

Large-scale screening of lipase acid deficiency in at risk population.

BACKGROUND: Lysosomal acid lipase deficiency (LALD, OMIM#278000) is a rare lysosomal disorder with an autosomal recessive inheritance. The main clinical manifestations are related to a progressive accumulation of cholesteryl esters, triglycerides or both within the lysosome in different organs such as the liver, spleen, and cardiovascular system. A wide range of clinical severity is associated with LALD including a severe very rare antenatal/neonatal/infantile phenotype named Wolman disease and a late-onset form named cholesteryl ester storage disease (CESD). METHODS: This study aimed to investigate a cohort of at-risk patients (4174) presenting with clinical or biological signs consistent with LALD using the assessment of LAL activity on dried blood spots. RESULTS: LAL activity was lower than 0.05 nmol/punch/L (cut-off: 0.12) in 19 patients including 13 CESD and 6 Wolman. Molecular study has been conducted in 17 patients and succeeded in identifying 34 mutated alleles. Fourteen unique variants have been characterized, 7 of which are novel. CONCLUSION: This study allowed to identify a series of patients and expanded the molecular spectrum knowledge of LALD. Besides, a new screening criteria grid based on the clinical/biological data from our study and the literature has been proposed in order to enhance the diagnosis rate in at risk populations.

Paroxysmal Dyskinesias Revealing 3-Hydroxy-Isobutyryl-CoA Hydrolase (HIBCH) Deficiency.

Paroxysmal dyskinesias (PD) are rare movement disorders characterized by recurrent attacks of dystonia, chorea, athetosis, or their combination, with large phenotypic and genetic heterogeneity. 3-Hydroxy-isobutyryl-CoA hydrolase (HIBCH) deficiency is a neurodegenerative disease characterized in most patients by a continuous decline in psychomotor abilities or a secondary regression triggered by febrile infections and metabolic crises.We describe two PD patients from two pedigrees, both carrying a homozygous c.913A > G, p.Thr305Ala mutation in the HIBCH gene, associated with an unusual clinical presentation. The first patient presented in the second year of life with right paroxysmal hemidystonia lasting for 30 minutes, without any loss of consciousness and without any triggering factor. The second patient has presented since the age of 3 recurrent exercise-induced PD episodes which have been described as abnormal equinovarus, contractures of the lower limbs, lasting for 1 to 4 hours, associated with choreic movements of the hands. Their neurological examination and metabolic screening were normal, while brain magnetic resonance imaging showed abnormal signal of the pallidi.We suggest that HIBCH deficiency, through the accumulation of metabolic intermediates of the valine catabolic pathway, leads to a secondary defect in respiratory chain activity and pyruvate dehydrogenase (PDH) activity and to a broad phenotypic spectrum ranging from Leigh syndrome to milder phenotypes. The two patients presented herein expand the spectrum of the disease to include unusual paroxysmal phenotypes and HIBCH deficiency should be considered in the diagnostic strategy of PD to enable adequate preventive treatment.

Clinical and biological characterization of 20 patients with TANGO2 deficiency indicates novel triggers of metabolic crises and no primary energetic defect.

TANGO2 disease is a severe inherited disorder associating multiple symptoms such as metabolic crises, encephalopathy, cardiac arrhythmias, and hypothyroidism. The mechanism of action of TANGO2 is currently unknown. Here, we describe a cohort of 20 French patients bearing mutations in the TANGO2 gene. We found that the main clinical presentation was the association of neurodevelopmental delay (n = 17), acute metabolic crises (n = 17) and hypothyroidism (n = 12), with a large intrafamilial clinical variability. Metabolic crises included rhabdomyolysis (15/17), neurological symptoms (14/17), and cardiac features (12/17; long QT (n = 10), Brugada pattern (n = 2), cardiac arrhythmia (n = 6)) that required intensive care. We show previously uncharacterized triggers of metabolic crises in TANGO2 patients, such as some anesthetics and possibly l-carnitine. Unexpectedly, plasma acylcarnitines, plasma FGF-21, muscle histology, and mitochondrial spectrometry were mostly normal. Moreover, in patients' primary myoblasts, palmitate and glutamine oxidation rates, and the mitochondrial network were also normal. Finally, we found variable mitochondrial respiration and defective clearance of oxidized DNA upon cycles of starvation and refeeding. We conclude that TANGO2 disease is a life-threatening disease that needs specific cardiac management and anesthesia protocol. Mechanistically, TANGO2 disease is unlikely to originate from a primary mitochondrial defect. Rather, we suggest that mitochondrial defects are secondary to strong extrinsic triggers in TANGO2 deficient patients.

Real-life use of videos in pediatric epilepsy consultations.

Paroxysmal events are usually not directly observed by physicians. The diagnosis remains challenging and relies mostly on the description of witnesses. The effectiveness of videos for seizure diagnosis has been validated by several studies, but their place in clinical practice is not yet clear. The aim of our study was to evaluate the real-life use of videos by child neurologists. We conducted a three-month prospective study in which child neurologists were asked to use a short questionnaire to evaluate all videos that were watched in their clinical practice for an initial diagnosis or during follow-up. A click-off meeting during the French pediatric neurology meeting allowed to recruit participants. A total of 165 questionnaires were completed by 15 physicians over the study period. The physicians were child neurologists working in secondary and tertiary/university hospitals, consulting children with epilepsy. Based on the evaluation of child neurologists, 51% of the videos consisted of epileptic seizures; 40%, nonepileptic paroxysmal events; and 9%, psychogenic nonepileptic seizures. Most of the videos were made on parental initiative. The use of video has modified the first diagnosis hypothesis in 35% of cases. The physicians' feelings regarding the interest of the video used during the diagnostic phase were similar to those of the video used during follow-up. It appears that videos have become a part of the epilepsy clinic and are helpful for diagnosis as well as during follow-up. Unfortunately, one of the limitations of this study is the absence of private practitioner.

PRPS1 loss-of-function variants, from isolated hearing loss to severe congenital encephalopathy: New cases and literature review.

We describe two sporadic and two familial cases with loss-of-function variants in PRPS1, which is located on the X chromosome and encodes phosphoribosyl pyrophosphate synthetase 1 (PRS-1). We illustrate the clinical variability associated with decreased PRS-1 activity, ranging from mild isolated hearing loss to severe encephalopathy. One of the variants we identified has already been reported with a phenotype similar to our patient's, whereas the other three were unknown. The clinical and biochemical information we provide will hopefully contribute to gain insight into the correlation between genotype and phenotype of this rare condition, both in females and in males. Moreover, our observation of a new family in which hemizygous males display hearing loss without any neurological or ophthalmological symptoms prompts us to suggest analysing PRPS1 in cases of isolated hearing loss. Eventually, PRPS1 variants should be considered as a differential diagnosis of mitochondrial disorders.

Early-onset epileptic encephalopathy related to germline PIGA mutations: A series of 5 cases.

The molecular diagnosis of early-onset epileptic encephalopathy (EOEE), an expanding field in child neurology, is becoming increasingly possible thanks to the widespread availability of next-generation sequencing and whole-exome sequencing. In the past 15 years, mutations in STXBP1, KCNQ2, SCN2A, SCN8A and numerous other genes have been reported, giving a more accurate insight for these rare diseases. Among these genes, germline mutations in Phosphatidyl Inositol Glycan A (PIGA) gene were first reported in 2012. Located on Xp22.2, PIGA is involved in the synthesis of GPI (glycosylphosphatidylinositol) which acts as a membrane anchor for different proteins: enzymes, adhesion molecules, regulation of the complement way, and co-receptor in transduction signal. Children suffering from this condition exhibit developmental delay with early-onset epilepsy, severe dysmorphic signs, multi-visceral anomalies and early death in the most severe forms. Here, we report five cases of germline PIGA mutations, with two missense mutations that have not been reported to date. We provide a new insight into the electroclinical phenotype. At the onset, epileptic spasms and focal-onset seizures with upper limbs and ocular involvements were present. Epilepsy proved pharmacoresistant in 4 out of 5 cases. Interictal EEG may be normal at the onset of epilepsy, but abnormalities in electroencephalographic studies were eventually present in all cases. Different types of seizures may be present simultaneously, and epileptic phenotypes evolve with aging.

Neonatal factors related to survival and intellectual and developmental outcome of patients with early-onset urea cycle disorders.

PURPOSE: We aimed to identify prognostic factors for survival and long-term intellectual and developmental outcome in neonatal patients with early-onset urea cycle disorders (UCD) experiencing hyperammonaemic coma. METHODS: We retrospectively analysed ammonia (NH3) and glutamine levels, electroencephalogram and brain images obtained during neonatal coma of UCD patients born between 1995 and 2011 and managed at a single centre and correlated them to survival and intellectual and developmental outcome. RESULTS: We included 38 neonates suffering from deficiencies of argininosuccinate synthetase (ASSD, N = 12), ornithine transcarbamylase (OTCD, N = 10), carbamoylphosphate synthetase 1 (CPSD, N = 7), argininosuccinate lyase (ASLD, N = 7), N-acetylglutamate synthase (NAGS, N = 1) or arginase (ARGD, N = 1). Symptoms occurred earlier in mitochondrial than in cytosolic UCD. Sixty-eight percent of patients survived, with a mean (standard deviation-SD) follow-up of 10.4 (5.3) years. Mortality was mostly observed in OTCD (N = 7/10) and CPSD (N = 4/7) patients. Plasma NH3 level during the neonatal period, expressed as area under the curve, but not glutamine level was associated with mortality (p = .044 and p = .610). 62.1% of the patients had normal intellectual and developmental outcome. Intellectual and developmental outcome tended to correlate with UCD subtype (p = .052). No difference in plasma NH3 or glutamine level during the neonatal period among developmental outcomes was identified. EEG severity was linked to UCD subtypes (p = .004), ammonia levels (p = .037), duration of coma (p = .043), and mortality during the neonatal period (p = .020). Status epilepticus was recorded in 6 patients, 3 of whom died neonatally, 1 developed a severe intellectual disability while the 2 last patients had a normal development. CONCLUSION: UCD subtypes differed by survival rate, intellectual and developmental outcome and EEG features in the neonatal period. Hyperammonaemia expressed as area under the curve was associated with survival but not with intellectual and developmental outcome whereas glutamine was not associated with one of these outcomes. Prognostic value of video-EEG monitoring and the association between status epilepticus and mortality should be assessed in neonatal hyperammonaemic coma in further studies.

Defining the phenotypic spectrum of SLC6A1 mutations.

OBJECTIVE: Pathogenic SLC6A1 variants were recently described in patients with myoclonic atonic epilepsy (MAE) and intellectual disability (ID). We set out to define the phenotypic spectrum in a larger cohort of SCL6A1-mutated patients. METHODS: We collected 24 SLC6A1 probands and 6 affected family members. Four previously published cases were included for further electroclinical description. In total, we reviewed the electroclinical data of 34 subjects. RESULTS: Cognitive development was impaired in 33/34 (97%) subjects; 28/34 had mild to moderate ID, with language impairment being the most common feature. Epilepsy was diagnosed in 31/34 cases with mean onset at 3.7 years. Cognitive assessment before epilepsy onset was available in 24/31 subjects and was normal in 25% (6/24), and consistent with mild ID in 46% (11/24) or moderate ID in 17% (4/24). Two patients had speech delay only, and 1 had severe ID. After epilepsy onset, cognition deteriorated in 46% (11/24) of cases. The most common seizure types were absence, myoclonic, and atonic seizures. Sixteen cases fulfilled the diagnostic criteria for MAE. Seven further patients had different forms of generalized epilepsy and 2 had focal epilepsy. Twenty of 31 patients became seizure-free, with valproic acid being the most effective drug. There was no clear-cut correlation between seizure control and cognitive outcome. Electroencephalography (EEG) findings were available in 27/31 patients showing irregular bursts of diffuse 2.5-3.5 Hz spikes/polyspikes-and-slow waves in 25/31. Two patients developed an EEG pattern resembling electrical status epilepticus during sleep. Ataxia was observed in 7/34 cases. We describe 7 truncating and 18 missense variants, including 4 recurrent variants (Gly232Val, Ala288Val, Val342Met, and Gly362Arg). SIGNIFICANCE: Most patients carrying pathogenic SLC6A1 variants have an MAE phenotype with language delay and mild/moderate ID before epilepsy onset. However, ID alone or associated with focal epilepsy can also be observed.

Long-term metabolic follow-up and clinical outcome of 35 patients with maple syrup urine disease.

BACKGROUND: Maple syrup urine disease (MSUD) is a rare disease that requires a protein-restricted diet for successful management. Little is known, however, about the psychosocial outcome of MSUD patients. This study investigates the relationship between metabolic and clinical parameters and psychosocial outcomes in a cohort of patients with neonatal-onset MSUD. METHODS: Data on academic achievement, psychological care, family involvement, and biochemical parameters were collected from the medical records of neonatal MSUD patients treated at Necker Hospital (Paris) between 1964 and 2013. RESULTS: Thirty-five MSUD patients with a mean age of 16.3 (2.1-49.0) years participated. Metabolic decompensations (plasma leucine >380 µmol/L) were more frequent during the first year of life and after 15 years, mainly due to infection and dietary noncompliance, respectively. Leucine levels increased significantly in adulthood: 61.5% of adults were independent and achieved adequate social and professional integration; 56% needed occasional or sustained psychological or psychiatric care (8/19, with externalizing, mood, emotional, and anxiety disorders being the most common). Patients needing psychiatric care were significantly older [mean and standard deviation (SD) 22.6 (7.7) years] than patients needing only psychological follow-up [mean (SD) 14.3 (8.9) years]. Patients with psychological follow-up experienced the highest lifetime number of decompensations; 45% of families had difficulty coping with the chronic disease. Parental involvement was negatively associated with the number of lifetime decompensations. CONCLUSION: Adults had increased levels of plasma leucine, consistent with greater chronic toxicity. Psychological care was associated with age and number of decompensations. In addition, parental involvement appeared to be crucial in the management of MSUD patients.

Neurocognitive profiles in MSUD school-age patients.

Maple syrup urine disease (MSUD), an inborn error of amino acids catabolism is characterized by accumulation of branched chain amino acids (BCAAs) leucine, isoleucine, valine and their corresponding alpha-ketoacids. Impact on the cognitive development has been reported historically, with developmental delays of varying degree. Currently, earlier diagnosis and improved management allow a better neurodevelopment, without requirement of special education. However, specific impairments can be observed, and so far, results of detailed neurocognitive assessments are not available. The aim of this study was to analyse neurocognitive profiles of French MSUD patients. This was a multicentre retrospective study on MSUD patients who underwent neurocognitive evaluation at primary school age. Twenty-one patients with classical neonatal onset MSUD were included. The patients' mean age at the time of evaluation was 8.7 years. The mean intellectual quotient (IQ) score was in the normal range (95.1 ± 12.6). In a subset of eight patients, a consistent developmental pattern of higher verbal than performance IQ was observed (mean of the difference 25.7 ± 8.7, p < 0.0001). No correlation could be established between this pattern and long-term metabolic balance (BCAA blood levels), or severity of acute metabolic imbalances, or leucine blood levels at diagnosis and time to toxin removal procedure. These data show that some MSUD patients may exhibit an abnormal neurocognitive profile with higher verbal than performance abilities. This might suggest an executive dysfunction disorder that would need to be further investigated by specialized testing. This pattern is important to detect in MSUD, as appropriate neuropsychological treatment strategies should be proposed.

Mutations in MDH2, Encoding a Krebs Cycle Enzyme, Cause Early-Onset Severe Encephalopathy.

MDH2 encodes mitochondrial malate dehydrogenase (MDH), which is essential for the conversion of malate to oxaloacetate as part of the proper functioning of the Krebs cycle. We report bi-allelic pathogenic mutations in MDH2 in three unrelated subjects presenting with early-onset generalized hypotonia, psychomotor delay, refractory epilepsy, and elevated lactate in the blood and cerebrospinal fluid. Functional studies in fibroblasts from affected subjects showed both an apparently complete loss of MDH2 levels and MDH2 enzymatic activity close to null. Metabolomics analyses demonstrated a significant concomitant accumulation of the MDH substrate, malate, and fumarate, its immediate precursor in the Krebs cycle, in affected subjects' fibroblasts. Lentiviral complementation with wild-type MDH2 cDNA restored MDH2 levels and mitochondrial MDH activity. Additionally, introduction of the three missense mutations from the affected subjects into Saccharomyces cerevisiae provided functional evidence to support their pathogenicity. Disruption of the Krebs cycle is a hallmark of cancer, and MDH2 has been recently identified as a novel pheochromocytoma and paraganglioma susceptibility gene. We show that loss-of-function mutations in MDH2 are also associated with severe neurological clinical presentations in children.