Liver glycogen storage diseases due to phosphorylase system deficiencies: Diagnosis thanks to non invasive blood enzymatic and molecular studies Anne Davit-Spraul a, ⁎, Monique Piraud b , Dries Dobbelaere c , Vassili Valayannopoulos d , Philippe Labrune e, f , Dalila Habes g , Olivier Bernard f, g , Emmanuel Jacquemin f, g, h , Christiane Baussan a a Biochemistry Unit, CHU Bicêtre, Assistance Publique - Hôpitaux de Paris (AP-HP), France b Laboratoire des Maladies Héréditaires du Métabolisme, Centre de Biologie Est, Hospices Civils de Lyon, France c Reference Center for Inherited Metabolic Diseases in child and adulthood, Hospital Jeanne de Flandre, France d Reference Center for Inherited Metabolic Diseases, CHU Necker, AP-HP, France e Pediatric Unit and National Reference Centre for Inherited Metabolic Liver Diseases, CHU Antoine Béclère, AP-HP, France f Faculty of Medicine Paris - Sud, University Paris - Sud 11, Paris, France g Pediatric Hepatology Unit and National Reference Centre for Biliary Atresia, CHU Bicêtre, AP-HP, France h INSERM U757, University Paris –Sud 11, Orsay, France abstract article info Article history: Received 8 April 2011 Received in revised form 11 May 2011 Accepted 11 May 2011 Available online 17 May 2011 Keywords: Glycogen Storage Disease type VI and IX PYGL PHKA2 PHKB PHKG2 Glycogen storage disease (GSD) due to a deficient hepatic phosphorylase system defines a genetically heterogeneous group of disorders that mainly manifests in children. We investigated 45 unrelated children in whom a liver GSD VI or IX was suspected on the basis of clinical symptoms including hepatomegaly, increased serum transaminases, postprandial lactatemia and/or mild fasting hypoglycemia. Liver phosphorylase and phosphorylase b kinase activities studied in peripheral blood cells allowed to suspect diagnosis in 37 cases but was uninformative in 5. Sequencing of liver phosphorylase genes was useful to establish an accurate diagnosis. Causative mutations were found either in the PYGL (11 patients), PHKA2 (26 patients), PHKG2 (three patients) or in the PHKB (three patients) genes. Eleven novel disease causative mutations, five missense (p.N188K, p.D228Y, p.P382L, p.R491H, p.L500R) and six truncating mutations (c.501_502ins361pb, c.528 + 2 T N C, c.856-29_c.1518 + 614del, c.1620 + 1 G N C, p.E703del and c.2313-1 G N T) were identified in the PYGL gene. Seventeen novel disease causative mutations, ten missense (p.A42P, p.Q95R, p.G131D, p.G131V, p.Q134R, p.G187R, p.G300V, p.G300A, p.C326Y, p.W820G) and seven truncating (c.537 + 5 G N A, p.G396DfsX28, p.Q404X, p.N653X, p.L855PfsX87, and two large deletions) were identified in the PHKA2 gene. Four novel truncating mutations (p.R168X, p.Q287X, p.I268PfsX12 and c.272-1 G N C) were identified in the PHKG2 gene and three (c.573_577del, p.R364X, c.2427 + 3A N G) in the PHKB gene. Patients with PHKG2 mutations evolved towards cirrhosis. Molecular analysis of GSD VI or IX genes allows to confirm diagnosis suspected on the basis of enzymatic analysis and to establish diagnosis and avoid liver biopsy when enzymatic studies are not informative in blood cells. © 2011 Elsevier Inc. All rights reserved. 1. Introduction Glycogen storage diseases (GSD) are inborn errors of glycogen metabolism, affecting either liver or muscle or both. The different types have been characterized according to their specific enzymatic defects along the pathway of glycogen breakdown [1–3]. While muscle GSDs affect muscle glycogen utilization during effort (leading to effort intolerance and muscle weakness), liver GSDs lead to hepatomegaly and hypoglycemia due to the lack of distribution of glucose to the organism. Beside more severe liver GSD type I and III (due to glucose-6-phosphatase and debranching enzyme defects respectively), a functional deficiency of liver phosphorylase system defines a genetically heterogeneous group of GSD with usually moderate symptoms which manifest mainly in childhood. Patients primarily present with hepatomegaly, moderate statural growth retardation and a rather good fasting tolerance. In most cases the disease course is benign, with attenuation of symptoms as the children grow up [1,4–6]. Nevertheless, in some cases the phenotype can be more severe and symptoms such as reduced fasting tolerance, severe growth retardation and/or cirrhosis may be observed [7]. Abnormal biological results include elevated serum transaminase Molecular Genetics and Metabolism 104 (2011) 137–143 Abbreviations: GSD, glycogen storage disease; Pase, phosphorylase; Phk, phosphorylase b kinase; LF, liver failure; ALT, alanine aminotransferase; AST, aspartate aminotransferase; GGT, gamma-glutamyl transferase; ULN, upper limit of normal range; SNP, single nucleotide polymorphism. ⁎ Corresponding author at: Service de Biochimie, Hôpital Bicêtre, 78, rue du Général Leclerc, Le Kremlin-Bicêtre, 94275 cedex, France. Fax: +33 1 45 21 35 74. E-mail address: anne.spraul@bct.aphp.fr (A. Davit-Spraul). 1096-7192/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.ymgme.2011.05.010 Contents lists available at ScienceDirect Molecular Genetics and Metabolism journal homepage: www.elsevier.com/locate/ymgme