Genotype and phenotype features and prognostic factors of neonatal-onset pyridoxine-dependent epilepsy: A systematic review

Pyridoxine-dependent epilepsy (PDE-ALDH7A1) is a rare autosomal recessive disorder due to a deficiency of α-aminoadipic semialdehyde dehydrogenase. This study aimed to systematically explore genotypic and phenotypic features and prognostic factors of neonatal-onset PDE. A literature search covering PubMed, Elsevier, and Web of Science was conducted from January 2006 to August 2023. We identified 56 eligible studies involving 169 patients and 334 alleles. The c.1279 G>C variant was the most common variant of neonatal-onset PDE (25.7 %). All patients were treated with pyridoxine; forty patients received dietary intervention therapy. 63.9 % of the patients were completely seizure-free; however, 68.6 % of the patients had neurodevelopmental delays. Additionally, homozygous c.1279 G>C variants were significantly associated with ventriculomegaly, abnormal white matter signal, and cysts (P<0.05). In contrast, homozygous c.1364 T>C was associated with clonic seizure (P=0.031). Pyridoxine used immediately at seizure onset was an independent protective factor for developmental delay (P=0.035; odds ratio [OR]: 3.14). Besides, pyridoxine used early in the neonatal period was a protective factor for language delay (P=0.044; OR: 4.59). In contrast, neonatal respiratory distress (P=0.001; OR: 127.44) and abnormal brain magnetic resonance imaging (P=0.049; OR: 3.64) were risk factors. Prenatal movement abnormality (P=0.041; OR: 20.56) and abnormal white matter signal (P=0.012; OR: 24.30) were risk factors for motor delay. Myoclonic seizure (P=0.023; OR: 7.13) and status epilepticus (P=0.000; OR: 9.93) were risk factors for breakthrough seizures. In conclusion, our study indicated that pyridoxine should be started immediately when unexplained neonatal seizures occur and not later than the neonatal period to prevent poor neurodevelopmental outcomes.

Update current understanding of neurometabolic disorders related to lysine metabolism

Lysine, as an essential amino acid, predominantly undergoes metabolic processes through the saccharopine pathway, whereas a smaller fraction follows the pipecolic acid pathway. Although the liver is considered the primary organ for lysine metabolism, it is worth noting that lysine catabolism also takes place in other tissues and organs throughout the body, including the brain. Enzyme deficiency caused by pathogenic variants in its metabolic pathway may lead to a series of neurometabolic diseases, among which glutaric aciduria type 1 and pyridoxine-dependent epilepsy have the most significant clinical manifestations. At present, through research, we have a deeper understanding of the multiple pathophysiological mechanisms related to these diseases, including intracerebral accumulation of neurotoxic metabolites, imbalance between GABAergic and glutamatergic neurotransmission, energy deprivation due to metabolites, and the dysfunction of antiquitin. Because of the complexity of these diseases, their clinical manifestations are also diverse. The early implementation of lysine-restricted diets and supplementation with arginine and carnitine has reported positive impacts on the neurodevelopmental outcomes of patients. Presently, there is more robust evidence supporting the effectiveness of these treatments in glutaric aciduria type 1 compared with pyridoxine-dependent epilepsy.

Timing of therapy and neurodevelopmental outcomes in 18 families with pyridoxine-dependent epilepsy

BACKGROUND

Seventy-five percent of patients with pyridoxine-dependent epilepsy due to α-aminoadipic semialdehyde dehydrogenase deficiency (PDE-ALDH7A1) suffer intellectual developmental disability despite pyridoxine treatment. Adjunct lysine reduction therapies (LRT), aimed at lowering putative neurotoxic metabolites, are associated with improved cognitive outcomes. However, possibly due to timing of treatment, not all patients have normal intellectual function.

METHODS

This retrospective, multi-center cohort study evaluated the effect of timing of pyridoxine monotherapy and pyridoxine with adjunct LRT on neurodevelopmental outcome. Patients with confirmed PDE-ALDH7A1 with at least one sibling with PDE-ALDH7A1 and a difference in age at treatment initiation were eligible and identified via the international PDE registry, resulting in thirty-seven patients of 18 families. Treatment regimen was pyridoxine monotherapy in ten families and pyridoxine with adjunct LRT in the other eight. Primary endpoints were standardized and clinically assessed neurodevelopmental outcomes. Clinical neurodevelopmental status was subjectively assessed over seven domains: overall neurodevelopment, speech/language, cognition, fine and gross motor skills, activities of daily living and behavioral/psychiatric abnormalities.

RESULTS

The majority of early treated siblings on pyridoxine monotherapy performed better than their late treated siblings on the clinically assessed domain of fine motor skills. For siblings on pyridoxine and adjunct LRT, the majority of early treated siblings performed better on clinically assessed overall neurodevelopment, cognition, and behavior/psychiatry. Fourteen percent of the total cohort was assessed as normal on all domains.

CONCLUSION

Early treatment with pyridoxine and adjunct LRT may be beneficial for neurodevelopmental outcome. When evaluating a more extensive neurodevelopmental assessment, the actual impairment rate may be higher than the 75% reported in literature.

TAKE- HOME MESSAGE

Early initiation of lysine reduction therapies adjunct to pyridoxine treatment in patients with PDE-ALDH7A1 may result in an improved neurodevelopmental outcome.

Clinical and biochemical outcome of a patient with pyridoxine-dependent epilepsy treated by triple therapy (pyridoxine supplementation, lysine-restricted diet, and arginine supplementation)

Pyridoxine-dependent epilepsy (PDE) is a recessive genetic disease characterized by epileptic encephalopathy with therapeutic response to pharmacological doses of pyridoxine and resistance to anti-epileptic treatments. The recent discovery in 2006 of the genetic defect antiquitin (ALDH7A1, OMIM #266100) has helped to understand the underlying mechanism, which is the accumulation of neurotoxic intermediates in the lysine catabolic pathway. The goal of the new therapeutic approach, termed triple therapy (TT) (pyridoxine, lysine-restricted diet and arginine supplementation), is to improve epilepsy control and neurocognitive development in patients with PDE. We present the 3-year treatment outcome for a child with PDE on pyridoxine treatment (started at age 5 months), lysine-restricted diet (started at age 17 months) and arginine supplementation therapy (started at age 19 months). The TT was well-tolerated with good compliance. No adverse events were reported. We observed a neurodevelopmental improvement, significantly fewer seizures, and a reduction of pipecolic acid (PA) as a biomarker of the illness. Our results show an improving clinical evolution, supporting and extending previous studies reporting efficacy of TT.

Is oxidative stress an overlooked player in pyridoxine-dependent epilepsy? A focused review

Pyridoxine-dependent epilepsy (PDE) is a rare autosomal recessive developmental and epileptic encephalopathy that is responsive to pharmacologic doses of vitamin B₆. The deficiency of antiquitin, an enzyme involved in the catabolism of lysine, is believed to be its key molecular basis. Research to date has tended to focus on two known catabolic pathways of lysine, namely, saccharopine and pipecolic acid. However, the occurrence of oxidative stress and the presence of its metabolites have been only briefly highlighted in the literature. Owing to the importance of the topic and its potential for future diagnosis, prognosis and therapy, this paper reviews the suggested mechanisms of oxidative stress in antiquitin deficiency along with the proposed reactions and intermediates, and finally, discusses the challenges and opportunities.

Cognitive and neurological outcome of patients in the Dutch pyridoxine-dependent epilepsy (PDE-ALDH7A1) cohort, a cross-sectional study

BACKGROUND

Pyridoxine monotherapy in PDE-ALDH7A1 often results in adequate seizure control, but neurodevelopmental outcome varies. Detailed long-term neurological outcome is unknown. Here we present the cognitive and neurological features of the Dutch PDE-ALDH7A1 cohort.

METHODS

Neurological outcome was assessed in 24 patients (age 1-26 years); classified as normal, complex minor neurological dysfunction (complex MND) or abnormal. Intelligence quotient (IQ) was derived from standardized IQ tests with five severity levels of intellectual disability (ID). MRI's and treatments were assessed.

RESULTS

Ten patients (42%) showed unremarkable neurological examination, 11 (46%) complex MND, and 3 (12%) cerebral palsy (CP). Minor coordination problems were identified in 17 (71%), fine motor disability in 11 (46%), posture/muscle tone deviancies in 11 (46%) and abnormal reflexes in 8 (33%). Six patients (25%) had an IQ > 85, 7 (29%) borderline, 7 (29%) mild, 3 (13%) moderate, and 1 severe ID. Cerebral ventriculomegaly on MRI was progressive in 11. Three patients showed normal neurologic exam, IQ, and MRI. Eleven patients were treated with pyridoxine only and 13 by additional lysine reduction therapy (LRT). LRT started at age <3 years demonstrated beneficial effect on IQ results in 3 patients.

DISCUSSION

Complex MND and CP occurred more frequently in PDE-ALDH7A1 (46% and 12%) than in general population (7% and 0.2%, Peters et al., 2011, Schaefer et al., 2008). Twenty-five percent had a normal IQ. Although LRT shows potential to improve outcomes, data are heterogeneous in small patient numbers. More research with longer follow-up via the International PDE Registry (www.pdeonline.org) is needed.

Pyridoxal in the Cerebrospinal Fluid May Be a Better Indicator of Vitamin B6-dependent Epilepsy Than Pyridoxal 5'-Phosphate

BACKGROUND

We aimed to demonstrate the biochemical characteristics of vitamin B6-dependent epilepsy, with a particular focus on pyridoxal 5'-phosphate and pyridoxal in the cerebrospinal fluid.

METHODS

Using our laboratory database, we identified patients with vitamin B6-dependent epilepsy and extracted their data on the concentrations of pyridoxal 5'-phosphate, pyridoxal, pipecolic acid, α-aminoadipic semialdehyde, and monoamine neurotransmitters. We compared the biochemical characteristics of these patients with those of other epilepsy patients with low pyridoxal 5'-phosphate concentrations.

RESULTS

We identified seven patients with pyridoxine-dependent epilepsy caused by an ALDH7A1 gene abnormality, two patients with pyridoxal 5'-phosphate homeostasis protein deficiency, and 28 patients with other epilepsies with low cerebrospinal fluid pyridoxal 5'-phosphate concentrations. Cerebrospinal fluid pyridoxal and pyridoxal 5'-phosphate concentrations were low in patients with vitamin B6-dependent epilepsy but cerebrospinal fluid pyridoxal concentrations were not reduced in most patients with other epilepsies with low cerebrospinal fluid pyridoxal 5'-phosphate concentrations. Increase in 3-O-methyldopa and 5-hydroxytryptophan was demonstrated in some patients with vitamin B6-dependent epilepsy, suggestive of pyridoxal 5'-phosphate deficiency in the brain.

CONCLUSIONS

Low cerebrospinal fluid pyridoxal concentrations may be a better indicator of pyridoxal 5'-phosphate deficiency in the brain in vitamin B6-dependent epilepsy than low cerebrospinal fluid pyridoxal 5'-phosphate concentrations. This finding is especially helpful in individuals with suspected pyridoxal 5'-phosphate homeostasis protein deficiency, which does not have known biomarkers.

Impact of missense mutations in the ALDH7A1 gene on enzyme structure and catalytic function

Certain mutations in the ALDH7A1 gene cause pyridoxine-dependent epilepsy (PDE), an autosomal recessive metabolic disease characterized by seizures, and in some cases, intellectual disability. The mutational spectrum of PDE is vast and includes over 70 missense mutations. This review summarizes the current state of biochemical and biophysical research on the impact of PDE missense mutations on the structure and catalytic activity of ALDH7A1. Paradoxically, some mutations that target active site residues have a relatively modest impact on structure and function, while those remote from the active site can have profound effects. For example, missense mutations targeting remote residues in oligomer interfaces tend to strongly impact catalytic function by inhibiting formation of the active tetramer. These results shows that it remains very difficult to predict the impact of missense mutations, even when the structure of the wild-type enzyme is known. Additional biophysical analyses of many more disease-causing mutations are needed to develop the rules for predicting the impact of genetic mutations on enzyme structure and catalytic function.

Electroclinical variability of pyridoxine-dependent epilepsy caused by ALDH7A1 gene mutations in four Taiwanese children

BACKGROUND

The aim of this study was to describe the electroclinical variability of four Taiwanese patients with pyridoxine-dependent epilepsy (PDE) caused by ALDH7A1 gene mutations.

METHODS

Demographic data, case histories, clinical seizure patterns, EEG features, neuroimaging findings, ALDH7A1 gene mutations, treatments, and neurodevelopmental outcomes of the four patients were collected and analyzed.

RESULTS

The four patients exhibited the first symptom between the ages of 6 days and 11 months. The age of diagnosis was between 2 months and 13 years 8 months. Patient 1 exhibited classical phenotype of PDE, neonatal onset epileptic encephalopathy. Patient 2 showed atypical phenotypes of intractable epilepsy with additional neurological and abdominal symptoms. Patients 3 and 4, who had normal neurodevelopment, had familial epilepsy with fever sensitivity. Patients 2, 3, and 4 had atypical phenotypes and showed seizure exacerbation during febrile infections. EEG features of patient 1 revealed alternating rhythmic discharges followed by electrodecremental episodes; while those of patients 2, 3, and 4 disclosed nonspecific findings or normal results. Administration of oral pyridoxine hydrochloride resulted in seizure cessation in patients 1, 3, and 4, and they achieved normal neurodevelopmental outcomes, but intractable epilepsy and profound mental retardation occurred in patient 2 as he was not diagnosed until he was 13 years and 8 months old.

CONCLUSION

Electroclinical features of PDE vary widely, including patients with normal neurodevelopment and normal or nonspecific EEG findings. To avoid delay in treatment, a therapeutic trial with pyridoxine hydrochloride should be performed in all cases of neonatal, infantile, and childhood refractory epilepsy until ALDH7A1 gene mutation-related PDE has been excluded. Pyridoxine treatment may show clinical effectiveness even in a relatively late stage, i.e., age older than one year.

Brain malformations associated to Aldh7a1 gene mutations: Report of a novel homozygous mutation and literature review

BACKGROUND

The ALDH7A1 gene is known to be responsible for autosomal recessive pyridoxine-dependent epilepsy (OMIM 266100). The phenotypic spectrum of ALDH7A1 mutations is very heterogeneous ranging from refractory epilepsy and neurodevelopmental delay, to multisystem neonatal disorder.

AIM

The present study aims at describing the phenotype associated with a novel homozygous ALDH7A1 mutation and the spectrum of brain malformations associated with pyridoxine-dependent epilepsy.

METHODS

We conducted a literature review on the Internet database Pubmed (up to November 2017) searching for ALDH7A1 mutations associated with brain malformations and brain MRI findings.

RESULTS

We present the case of two siblings, children of related parents. The proband presented neonatal focal seizures not responding to conventional antiepileptic drugs. Electroencephalography showed a suppression burst pattern and several multifocal ictal patterns, responsive to pyridoxine. Brain MRI was normal. Molecular analysis by targeted next-generation sequencing panel for epileptic encephalopathy disclosed a homozygous missense mutation of ALDH7A1. The same mutation was then found in a stored sample of DNA from peripheral blood of an older sister dead 3 years earlier. This girl presented a complex brain malformation diagnosed with a foetal MRI and had neonatal refractory seizures with suppression burst pattern. She died at 6 months of age.

LITERATURE REVIEW

The brain abnormalities most frequently reported in pyridoxine-dependent epilepsy include: agenesia/hypoplasia of the corpus callosum, not specific white matter abnormalities, large cisterna magna, ventriculomegaly, haemorrhages, cerebellum hypoplasia/dysplasia, and, more rarely, dysplasia of the brainstem and hydrocephalus.

DISCUSSION AND CONCLUSIONS

ALDH7A1 mutations have been associated to different brain abnormalities, documented by MRI only in few cases. The study cases expand the clinical spectrum of ALDH7A1 associated conditions, suggesting to look for ALDH7A1 mutations not only in classical phenotypes but also in patients with brain malformations, mainly if there is a response to a pyridoxine trial.

Hydrocephalus in pyridoxine-dependent epilepsy: New case and literature review

INTRODUCTION

Pyridoxine-dependent epilepsy (PDE) is a rare disorder of the lysine metabolism, characterized by a pharmacoresistant epileptic encephalopathy that usually begins in the neonatal period. However, its phenotypic spectrum is wide and not limited to seizures. We report a new case of PDE who developed hydrocephalus, along with an exhaustive review of the literature.

CASE REPORT

Our patient presented with seizures at 13 h of life. Antiepileptic drugs, vitamins and cofactors were required to achieve seizure control. Laboratory tests were congruent with PDE. She remained seizure-free until age five months, when seizures reappeared in the context of increasing head size and irritability. A cranial ultrasound showed hydrocephalus, for which she underwent ventriculoperitoneal shunting.

DISCUSSION

Seven other patients with same features have been previously reported. Seizure onset occurred within the first 7 days in all patients. Most of the children developed hydrocephalus at 6-7 months of age. In 4 out of 7 a genetic mutation was identified, despite the accurate etiology of hydrocephalus was unknown in most of them. The case we report behaved similarly to the others previously described. We postulate that the pathogenesis of this complication could be related to the high expression of antiquitin in choroid plexus epithelium, where the cerebrospinal fluid is produced.

CONCLUSIONS

patients with PDE should be closely monitored, since they may present severe complications. We highlight the development of hydrocephalus, an uncommon but potentially life-threatening problem reported in 8 patients up to present time.

Phenotype, biochemical features, genotype and treatment outcome of pyridoxine-dependent epilepsy

We report treatment outcome of eleven patients with pyridoxine-dependent epilepsy caused by pathogenic variants in ALDH7A1 (PDE-ALDH7A1). We developed a clinical severity score to compare phenotype with biochemical features, genotype and delays in the initiation of pyridoxine. Clinical severity score included 1) global developmental delay/ intellectual disability; 2) age of seizure onset prior to pyridoxine; 3) current seizures on treatment. Phenotype scored 1-3 = mild; 4-6 = moderate; and 7-9 = severe. Five patients had mild, four patients had moderate, and two patients had severe phenotype. Phenotype ranged from mild to severe in eight patients (no lysine-restricted diet in the infantile period) with more than 10-fold elevated urine or plasma α-AASA levels. Phenotype ranged from mild to moderate in patients with homozygous truncating variants and from moderate to severe in patients with homozygous missense variants. There was no correlation between severity of the phenotype and the degree of α-AASA elevation in urine or genotype. All patients were on pyridoxine, nine patients were on arginine and five patients were on the lysine-restricted diet. 73% of the patients became seizure free on pyridoxine. 25% of the patients had a mild phenotype on pyridoxine monotherapy. Whereas, 100% of the patients, on the lysine-restricted diet initiated within their first 7 months of life, had a mild phenotype. Early initiation of lysine-restricted diet and/or arginine therapy likely improved neurodevelopmental outcome in young patients with PDE-ALDH7A1.

Impact of disease-Linked mutations targeting the oligomerization interfaces of aldehyde dehydrogenase 7A1

Aldehyde dehydrogenase 7A1 (ALDH7A1) is involved in lysine catabolism, catalyzing the oxidation of α-aminoadipate semialdehyde to α-aminoadipate. Certain mutations in the ALDH7A1 gene, which are presumed to reduce catalytic activity, cause an autosomal recessive seizure disorder known as pyridoxine-dependent epilepsy (PDE). Although the genetic association between ALDH7A1 and PDE is well established, little is known about the impact of PDE-mutations on the structure and catalytic function of the enzyme. Herein we report the first study of the molecular consequences of PDE mutations using purified ALDH7A1 variants. Eight variants, with mutations in the oligomer interfaces, were expressed in Escherichia coli: P78L, G83E, A129P, G137V, G138V, A149E, G255D, and G263E. All but P78L and G83E were soluble and could be purified. All six soluble mutants were catalytically inactive. The impact of the mutations on oligomerization was assessed by analytical ultracentrifugation. Wild-type ALDH7A1 is shown to exist in a dimer-tetramer equilibrium with a dissociation constant of 16 μM. In contrast to the wild-type enzyme, the variants reside in monomer-dimer equilibria and are apparently incapable of forming a tetrameric species, even at high enzyme concentration. The available evidence suggests that they are misfolded assemblies lacking the three-dimensional structure required for catalysis.

Current knowledge for pyridoxine-dependent epilepsy: a 2016 update

Pyridoxine-dependent epilepsy (PDE) is a rare genetic condition characterized by intractable and recurrent neonatal seizures that are uniquely alleviated by high doses of pyridoxine (vitamin B6). This recessive disease is caused by mutations in ALDH7A1, a gene encoding Antiquitin, an enzyme central to lysine degradation. This results in the pathogenic accumulation of the lysine intermediates Aminoadipate Semialdehyde (AASA) and its cyclic equilibrium form Piperideine-6-carboxylate (P6C) in body fluids; P6C reacts with pyridoxal-5'-phosphate (PLP, the active form of vitamin B6) causing its inactivation and leading to pyridoxine-dependent seizures. While PDE is responsive to pharmacological dosages of pyridoxine, despite lifelong supplementation, neurodevelopment delays are observed in >75% of PDE cases. Thus, adjunct treatment strategies are emerging to both improve seizure control and moderate the delays in cognition. These adjunctive therapies, lysine restriction and arginine supplementation, separately or in combination (with pyridoxine thus termed 'triple therapy'), have shown promising results and are recommended in all PDE patients. Other new therapeutic strategies currently in preclinical phase of study include antisense therapy and substrate reduction therapy. We present here a comprehensive review of current treatment options as well as PDE phenotype, differential diagnosis, current management and views upon the future of PDE research.

Pyridoxine-dependent epilepsy: report on three families with neuropathology

Pyridoxine-dependent epilepsy (PDE) is a pharmacoresistant epileptogenic encephalopathy controlled by pyridoxine supplementation at pharmacological doses. Despite supplementation, the long-term outcome is often poor possibly because of recurrent seizures and developmental structural brain abnormalities. We report on five patients with PDE from three unrelated families. The diagnosis was confirmed by ALDH7A1 sequencing, which allowed for the characterization of two homozygous variations [NM_001182.3:c.1279G > C - p.(Glu427Gln) and c.834G > A - p.(Val278Val)]. Brain autopsy was conducted for one untreated patient with molecularly confirmed antiquitin deficiency. Macroscopic and histological examination revealed a combination of lesions resulting from recurrent seizures and consisting of extensive areas of cortical necrosis, gliosis, and hippocampic sclerosis. The examination also revealed developmental abnormalities including corpus callosum dysgenesis and corticospinal pathfinding anomalies. This case is the second to be reported in the literature, and our findings show evidence that antiquitin is required for normal brain development and functioning. Despite prophylactic prenatal pyridoxine supplementation during the last trimester of pregnancy in one of the three families and sustained pyridoxine treatment in three living patients, the clinical outcome remained poor with delayed acquisition of neurocognitive skills. Combined therapy (pyridoxine/arginine supplementation and lysine-restricted diet) should be considered early in the course of the disease for a better long-term outcome. Enhanced knowledge of PDE features is required to improve treatment strategies.

Effect of dietary lysine restriction and arginine supplementation in two patients with pyridoxine-dependent epilepsy

Pyridoxine-Dependent Epilepsy (PDE) is a recessive disorder caused by deficiency of α-aminoadipic semialdehyde dehydrogenase in the catabolic pathway of lysine. It is characterized by intractable seizures controlled by the administration of pharmacological doses of vitamin B6. Despite seizure control with pyridoxine, intellectual disability and developmental delays are still observed in some patients with PDE, likely due to the accumulation of toxic intermediates in the lysine catabolic pathway: alpha-aminoadipic semialdehyde (AASA), delta-1-piperideine-6-carboxylate (P6C), and pipecolic acid. Here we evaluate biochemical and clinical parameters in two PDE patients treated with a lysine-restricted diet and arginine supplementation (100-150mg/kg), aimed at reducing the levels of PDE biomarkers. Lysine restriction resulted in decreased accumulation of PDE biomarkers and improved development. Plasma lysine but not plasma arginine, directly correlated with plasma levels of AASA-P6C (p<0.001, r(2)=0.640) and pipecolic acid (p<0.01, r(2)=0.484). In addition, plasma threonine strongly correlated with the levels of AASA-P6C (p<0.0001, r(2)=0.732) and pipecolic acid (p<0.005, r(2)=0.527), suggesting extreme sensitivity of threonine catabolism to pyridoxine availability. Our results further support the use of dietary therapies in combination with pyridoxine for the treatment of PDE.

A cohort study of pyridoxine-dependent epilepsy and high prevalence of splice site IVS11+1G>A mutation in Chinese patients

PURPOSE

Pyridoxine-dependent epilepsy (PDE) is a rare autosomal recessive disorder caused by mutations of the ALDH7A1 gene. We aimed to analyze the relations between the clinical diagnosis and treatment of PDE and ALDH7A1 gene mutations in Chinese PDE patients.

METHODS

The clinical manifestations, diagnosis and treatment were observed in a cohort of PDE patients with early onset of seizure. Video-electroencephalogram (VEEG) and magnetic resonance imaging (MRI) were performed. The mutation of ALDH7A1 gene was analyzed.

RESULTS

Of eight patients, six were males and two were females. Age of seizure onset ranged from 1 to 100 days and 75% patients presented with seizures in the neonatal period. All patients showed different degrees of developmental delay. EEGs showed focal or multifocal discharges, or were normal. Molecular analysis revealed 10 ALDH7A1 mutations, including 2 splice site mutations. Five patients had mutation at IVS11+1G>A site, six patients had missense mutations, one with nonsense mutation and another patient had 9-bp genomic deletion mutation. Among them, two mutations were first time reported.

CONCLUSIONS

Seizure onset was in neonatal or early infantile period in our PDE patients. Early recognition and diagnosis of the disease is necessary for early intervention and improve cognitive development in the later life. In this study, on the molecular level, we also identified the splice site mutation IVS11+1G>A as a high prevalence mutation site with a frequency of 31.25% (5 of 16 alleles) in Chinese PDE patients.

Seizure recurrence following pyridoxine withdrawal in a patient with pyridoxine-dependent epilepsy

Pyridoxine-dependent epilepsy (PDE) is an autosomal recessive disorder characterized by early onset and recurrent seizures that can be controlled by a high dose of pyridoxine. PDE is caused by mutations in ALDH7A1, which encodes antiquitin. Antiquitin converts α-aminoadipic semialdehyde to α-aminoadipic acid. Seizure recurrence after pyridoxine withdrawal is a criterion for diagnosis, but PDE can be diagnosed conclusively by genetic testing for mutations in the ALDH7A1 gene. In this case study, we report the long-term follow-up of a patient suspected with PDE. She experienced prolonged generalized tonic seizures and was hospitalized in an intensive care unit following pyridoxine withdrawal. Later, we identified a compound heterozygous mutation, c.1216G>A, p.Gly406Arg, and a novel splice donor site mutation, IVS9+5G>A. Confirmation of these mutations would have prevented an unsafe withdrawal test. This case suggests the importance of the genetic determination of PDE to avoid the diagnostic withdrawal of pyridoxine.

Preliminary investigation of the use of newborn dried blood spots for screening pyridoxine-dependent epilepsy by LC-MS/MS

α-AASA and P6C were measured retrospectively in original newborn DBS of five patients with PDE using a LC-MS/MS method we developed previously. Both α-AASA and P6C were elevated markedly in the three newborn DBS stored at -20°C. At room temperature, α-AASA and P6C in DBS appeared stable for 3 days and then decreased by up to 70% after 14 days but remained much higher than control, indicating newborn screening for PDE is feasible.