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.

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.

Novel therapy for pyridoxine dependent epilepsy due to ALDH7A1 genetic defect: L-arginine supplementation alternative to lysine-restricted diet

BACKGROUND AND HYPOTHESIS

Pyridoxine dependent epilepsy (PDE) due to mutations in the ALDH7A1 gene (PDE-ALDH7A1) is caused by α-aminoadipic-semialdehyde-dehydrogenase enzyme deficiency in the lysine pathway resulting in the accumulation of α-aminoadipic acid semialdehyde (α-AASA). Classical presentation is neonatal intractable seizures with a dramatic response to pyridoxine. Pyridoxine therapy does not prevent developmental delays in the majority of the patients. We hypothesized that L-arginine supplementation will decrease accumulation of α-AASA by competitive inhibition of lysine transport into the central nervous system and improve neurodevelopmental and neurocognitive functions in PDE-ALDH7A1.

METHODS

A 12-year-old male with PDE-ALDH7A1 was treated with l-arginine supplementation as an innovative therapy. Treatment outcome was monitored by cerebral-spinal-fluid (CSF) α-AASA measurements at baseline, 6th and 12th months of therapy. Neuropsychological assessments were performed at baseline and 12th months of therapy.

RESULTS

L-arginine therapy was well tolerated without side effects. CSF α-AASA was decreased 57% at 12th months of therapy. Neuropsychological assessments revealed improvements in general abilities index from 108 to 116 and improvements in verbal and motor functioning at 12th months of therapy.

CONCLUSION

The short-term treatment outcome of this novel L-arginine supplementation therapy for PDE-ALDH7A1 was successful for biochemical and neurocognitive improvements.