Barbara Plecko1, Karl Paul, Philippa Mills, Peter Clayton, Eduard Paschke, Oliver Maier, Oswald Hasselmann, Gudrun Schmiedel, Simone Kanz, Mary Connolly, Nicole Wolf, Eduard Struys, Sylvia Stockler, Lucia Abela, Doris Hofer. 1. From the Department of Pediatrics (B.P., L.A.), Division of Child Neurology, University Hospital Zurich, Switzerland; the Department of Pediatrics (B.P.), Division of Neurology and Inborn Errors of Metabolism, Medical University Graz, Austria; radiz-"Rare Disease Initiative Zurich, Clinical Research Priority Program for Rare Diseases University of Zurich" (B.P., L.A.); CRC Clinical Research Center (B.P.), University Childrens' Hospital Zurich, Switzerland; the Laboratory of Metabolic Diseases (K.P., E.P., D.H.), Department of Pediatrics, University Hospital Graz, Austria; UCL Institute of Child Health (P.M., P.C.), Clinical and Molecular Genetics Unit, London, UK; Childrens Hospital St. Gallen (O.M., O.H.), Switzerland; the Department of Pediatrics (G.H.), Klinikum Esslingen; the Department of Pediatrics (S.K.), St. Marien Hospital, Landshut, Germany; the Division of Child Neurology (M.C.) and Division of Biochemical Diseases (S.S.), Department of Pediatrics, University of British Columbia, Vancouver, Canada; the Department of Pediatrics, Division of Child Neurology (N.W.), VU University Medical Center and Neuroscience Campus Amsterdam; and the Department of Clinical Chemistry (E.S.), Vrije Universiteit Amsterdam, the Netherlands.
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.
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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Authors: Déborah Mathis; Lucia Abela; Monique Albersen; Céline Bürer; Lisa Crowther; Karin Beese; Hans Hartmann; Levinus A Bok; Eduard Struys; Sorina M Papuc; Anita Rauch; Martin Hersberger; Nanda M Verhoeven-Duif; Barbara Plecko Journal: J Inherit Metab Dis Date: 2016-06-24 Impact factor: 4.982
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