title: Pediatric patient with hyperketotic hypoglycemia diagnosed with glycogen synthase deficiency due to the novel homozygous mutation in GYS2.
abstract: BACKGROUND
  Glycogen synthase deficiency (glycogen storage disease 0 - GSD 0) caused by mutations in the GYS2 gene is characterized by a lack of glycogen synthesis in the liver. It is a rare condition of disturbed glycogen homeostasis in the liver with less than 30 cases reported in the literature so far.
  
  
  METHODS
  We report a 9 year old boy diagnosed with GSD 0 due to the newly identified, highly pathogenic homozygous mutation: NM_021957.3:p.Phe574Leu/c.1720T > C in ex. 14. A random, asymptomatic hypoglycemia with ketonuria was found in this patient at the age of 7. His developmental parameters were within normal ranges. Oral glucose tolerance test showed normal baseline blood levels of glucose, insulin and lactate, and their increase following glucose intake. Eight-hour fasting plasma glucose test, revealed glucose blood level of 34 mg/dl with no clinical symptoms. The results of these tests suggested GSD 0. Molecular analysis of the GYS2 gene was not feasible, but this particular gene was included in the panel of hypoglycemia of whole exome sequencing (WES) which was at our disposal.
authors.affiliation: Department of Pediatrics, Nutrition and Metabolic Disorders, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Edyta
authors.initials: E
authors.lastname: Szymańska
authors.affiliation: Department of Pediatrics, Nutrition and Metabolic Disorders, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Dariusz
authors.initials: D
authors.lastname: Rokicki
authors.affiliation: Department of Endocrinology and Diabetology, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Urszula
authors.initials: U
authors.lastname: Wątrobinska
authors.affiliation: Department of Medical Genetics, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Ciara
authors.affiliation: Department of Medical Genetics, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Paulina
authors.initials: P
authors.lastname: Halat
authors.affiliation: Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland.
authors.forename: Rafał
authors.initials: R
authors.lastname: Płoski
authors.affiliation: Department of Pediatrics, Nutrition and Metabolic Disorders, The Children's Memorial Health Institute, Warsaw, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Tylki-Szymańka
keywords: Glycogen storage disease 0; Glycogen synthase deficiency; Hypoglycemia