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Pyridoxine responsiveness in novel mutations of the PNPO gene


Abstract

OBJECTIVE: To determine whether patients with pyridoxine-responsive seizures but normal biomarkers for antiquitin deficiency and normal sequencing of the ALDH7A1 gene may have PNPO mutations.
METHODS: We sequenced the PNPO gene in 31 patients who fulfilled the above-mentioned criteria.
RESULTS: We were able to identify 11 patients carrying 3 novel mutations of the PNPO gene. In 6 families, a homozygous missense mutation p.Arg225His in exon 7 was identified, while 1 family was compound heterozygous for a novel missense mutation p.Arg141Cys in exon 5 and a deletion c.279_290del in exon 3. Pathogenicity of the respective mutations was proven by absence in 100 control alleles and expression studies in CHO-K1 cell lines. The response to pyridoxine was prompt in 4, delayed in 2, on EEG only in 2, and initially absent in another 2 patients. Two unrelated patients homozygous for the p.Arg225His mutation experienced status epilepticus when switched to pyridoxal 5'-phosphate (PLP).
CONCLUSIONS: This study challenges the paradigm of exclusive PLP responsiveness in patients with pyridoxal 5'-phosphate oxidase deficiency and underlines the importance of consecutive testing of pyridoxine and PLP in neonates with antiepileptic drug-resistant seizures. Patients with pyridoxine response but normal biomarkers for antiquitin deficiency should undergo PNPO mutation analysis.

Abstract

OBJECTIVE: To determine whether patients with pyridoxine-responsive seizures but normal biomarkers for antiquitin deficiency and normal sequencing of the ALDH7A1 gene may have PNPO mutations.
METHODS: We sequenced the PNPO gene in 31 patients who fulfilled the above-mentioned criteria.
RESULTS: We were able to identify 11 patients carrying 3 novel mutations of the PNPO gene. In 6 families, a homozygous missense mutation p.Arg225His in exon 7 was identified, while 1 family was compound heterozygous for a novel missense mutation p.Arg141Cys in exon 5 and a deletion c.279_290del in exon 3. Pathogenicity of the respective mutations was proven by absence in 100 control alleles and expression studies in CHO-K1 cell lines. The response to pyridoxine was prompt in 4, delayed in 2, on EEG only in 2, and initially absent in another 2 patients. Two unrelated patients homozygous for the p.Arg225His mutation experienced status epilepticus when switched to pyridoxal 5'-phosphate (PLP).
CONCLUSIONS: This study challenges the paradigm of exclusive PLP responsiveness in patients with pyridoxal 5'-phosphate oxidase deficiency and underlines the importance of consecutive testing of pyridoxine and PLP in neonates with antiepileptic drug-resistant seizures. Patients with pyridoxine response but normal biomarkers for antiquitin deficiency should undergo PNPO mutation analysis.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Children's Hospital Zurich > Medical Clinic
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:22 April 2014
Deposited On:05 Feb 2015 15:40
Last Modified:14 Feb 2018 22:35
Publisher:Lippincott Williams & Wilkins
ISSN:0028-3878
OA Status:Green
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:https://doi.org/10.1212/WNL.0000000000000344
PubMed ID:24658933

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