Systemic Manifestations in Pyridox(am)ine Phosphate Oxidase (PNPO) Deficiency

Publication date: Available online 3 June 2017
Source:Pediatric Neurology
Author(s): Réjean M. Guerriero, Archana A. Patel, Brian Walsh, Fiona M. Baumer, Ankoor S. Shah, Jurriaan M. Peters, Lance H. Rodan, Pankaj B. Agrawal, Phillip L. Pearl, Masanori Takeoka
ObjectivePyridoxine is converted to its biologically active form, pyridoxal-5-phosphate (P5P) by the enzyme pyridox(am)ine oxidase (PNPO), and serves as a cofactor in nearly 200 reactions in the central nervous system (CNS). PNPO deficiency leads to P5P dependent epilepsy, typically a neonatal or infantile onset epileptic encephalopathy treatable with P5P or in some cases pyridoxine. Following identification of retinopathy in a patient with PNPO deficiency that was reversible with P5P therapy, we report the systemic manifestations of PNPO deficiency..MethodsA series of six patients with confirmed homozygous PNPO mutations were identified who presented to our center over the course of two years for phenotyping of neurologic and systemic manifestations.ResultsFive out of six were born prematurely, three had anemia and failure to thrive, and two had elevated alkaline phosphatase. A movement disorder was observed in two children and a reversible retinopathy was observed in the most severely affected infant. All subjects had neonatal onset epilepsy and were on a continuum of developmental delay to profound encephalopathy. EEG features included background slowing and disorganization, absent sleep features, and multifocal and generalized epileptiform discharges. All the affected probands carried homozygous PNPO mutations (c.674 G>T, c.686 G>A and c.352G>A).ConclusionIn addition to the well described epileptic encephalopathy, PNPO deficiency causes a range of neurologic and systemic manifestations. A movement disorder, developmental delay and encephalopathy, as well as retinopathy, anemia, and failure to thrive add to the broadening clinical spectrum of P5P dependent epilepsy.



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