title: The natural history of glycogen storage disease types VI and IX: Long-term outcome from the largest metabolic center in Canada.
abstract: OBJECTIVE
  Glycogen storage disease (GSD) types VI and IX are caused by phosphorylase system deficiencies. To evaluate the natural history and long-term treatment outcome of the patients with GSD-VI and -IX, we performed an observational retrospective case study of 21 patients with confirmed diagnosis of GSD-VI or -IX.
  
  
  METHODS
  All patients with GSD-VI or -IX, diagnosed at The Hospital for Sick Children, were included. Electronic and paper charts were reviewed for clinical features, biochemical investigations, molecular genetic testing, diagnostic imaging, long-term outcome and treatment by two independent research team members. All information was entered into an Excel database.
  
  
  RESULTS
  We report on the natural history and treatment outcomes of the 21 patients with GSD-VI and -IX and 16 novel pathogenic mutations in the PHKA2, PHKB, PHKG2 and PYGL genes. We report for the first time likely liver adenoma on liver ultrasound and liver fibrosis on liver biopsy specimens in patients with GSD-VI and mild cardiomyopathy on echocardiography in patients with GSD-VI and -IXb.
  
  
  CONCLUSIONS
  We recommend close monitoring in all patients with GSD-VI and -IX for the long-term liver and cardiac complications. There is a need for future studies if uncooked cornstarch and high protein diet would be able to prevent long-term complications of GSD-VI and -IX.
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada; Medical University of Vienna, Department of Pediatric and Adolescent Medicine, Vienna, Austria.
authors.forename: Anne
authors.initials: A
authors.lastname: Roscher
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
authors.forename: Jaina
authors.initials: J
authors.lastname: Patel
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
authors.forename: Stacy
authors.initials: S
authors.lastname: Hewson
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Nagy
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada; Department of Pediatrics & Biochemical Genetics, Rady Children's Hospital-San Diego, University of California, San Diego, CA, USA.
authors.forename: Annette
authors.initials: A
authors.lastname: Feigenbaum
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Kronick
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
authors.forename: Julian
authors.initials: J
authors.lastname: Raiman
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada; Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schulze
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada.
authors.forename: Komudi
authors.initials: K
authors.lastname: Siriwardena
authors.affiliation: Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Toronto, ON, Canada; Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada. Electronic address: saadet.mahmutoglu@sickkids.ca.
authors.forename: Saadet
authors.initials: S
authors.lastname: Mercimek-Mahmutoglu
mesh_terms: D000293:Adolescent; D002170:Canada; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D005260:Female; D006008:Glycogen Storage Disease / Q000150:complications / Q000235:genetics / Q000628:therapy; D006013:Glycogen Storage Disease Type VI / Q000150:complications / Q000235:genetics* / Q000628:therapy; D006801:Humans; D008103:Liver Cirrhosis / Q000235:genetics; D008297:Male; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Glycogen storage disease types VI and IX; Liver fibrosis; Phosphorylase enzyme deficiency; Phosphorylase kinase enzyme deficiency; Uncooked cornstarch