Pyridoxine-Dependent Epilepsy and Metabolic Disorders

Pyridoxine-dependent epilepsy (PDE) is a rare neurometabolic syndrome characterised by seizures that fail to respond to standard antiepileptic drugs but remit upon administration of vitamin B6, either as pyridoxine or its active coenzyme form, pyridoxal 5′-phosphate (PLP). The condition arises primarily from inborn errors affecting PLP synthesis, recycling or distribution. Chief among these are biallelic mutations in ALDH7A1, encoding antiquitin, which lead to accumulation of neurotoxic lysine-catabolites; variants in PNPO, the enzyme converting pyridoxine 5′-phosphate to PLP; and defects in the PLP homeostasis protein (PLPBP), implicated in intracellular PLP trafficking. Deficient PLP availability undermines the function of more than 140 PLP-dependent enzymes, including glutamic acid decarboxylase, resulting in impaired γ-aminobutyric acid synthesis, excitatory-inhibitory imbalance and early-onset epileptic encephalopathy. Hallmarks include neonatal or infantile seizures, developmental delay and elevated metabolic markers such as α-aminoadipic semialdehyde or pipecolic acid. Early genetic and biochemical diagnosis is critical to initiate tailored therapy—high-dose pyridoxine or PLP supplementation, often combined with dietary lysine restriction—to control seizures, although long-term neurocognitive outcomes vary. Beyond epilepsy, these insights underscore the broader role of vitamin B6 in amino acid metabolism, mitochondrial function and cellular antioxidant defence, highlighting avenues for novel therapeutic interventions across a spectrum of metabolic disorders.

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Pyridoxine-Dependent Epilepsy and Metabolic Disorders publication trend

The graph below shows the total number of articles in pyridoxine-dependent epilepsy and metabolic disorders across all publications each year (not limited to Nature Index journals).

Technical terms

Pyridoxine-dependent epilepsy (PDE): A form of early-onset epilepsy that responds specifically to vitamin B6 supplementation due to enzyme defects in B6 metabolism.

Pyridoxal 5′-phosphate (PLP): The biologically active form of vitamin B6, serving as a cofactor for numerous enzymes in amino acid and neurotransmitter metabolism.

Antiquitin (ALDH7A1): An enzyme in the lysine degradation pathway; its deficiency leads to accumulation of neurotoxic intermediates causing PDE.

Pyridox(am)ine 5′-phosphate oxidase (PNPO): An enzyme that oxidises pyridoxine and pyridoxamine phosphates to PLP; mutations impair PLP synthesis and cause seizures.

PLP homeostasis protein (PLPBP): A protein thought to bind and deliver PLP within cells; its deficiency disrupts PLP availability and mitochondrial metabolism.

References

1. Disorders affecting vitamin B6 metabolism. Journal of Inherited Metabolic Disease (2019).
2. Identification of the pyridoxal 5′‐phosphate allosteric site in human pyridox(am)ine 5′‐phosphate oxidase. Protein Science (2024).
3. Maintenance of cellular vitamin B6 levels and mitochondrial oxidative function depend on pyridoxal 5′-phosphate homeostasis protein. Journal of Biological Chemistry (2023).
4. New insights into human lysine degradation pathways with relevance to pyridoxine‐dependent epilepsy due to antiquitin deficiency. Journal of Inherited Metabolic Disease (2019).