title: Two patients with GMPPB mutation: The overlapping phenotypes of limb-girdle myasthenic syndrome and limb-girdle muscular dystrophy dystroglycanopathy.
abstract: Mutations in the guanosine diphosphate-mannose pyrophosphorylase-B gene (GMPPB) have been identified in congenital muscular dystrophies, limb-girdle muscular dystrophy (LGMD2T), and congenital myasthenic syndromes (CMSs); overall, 41 patients have been described.
  
  
  
  Two patients presented with a myasthenic syndrome (patient 1; 74 years old) and rhabdomyolysis (patient 2; 23 years old). Examinations included repetitive nerve stimulation, muscle biopsy and whole-body MRI (WBMRI); next generation sequencing facilitated diagnosis.
  
  
  
  We identified the following GMPPB mutations: c.79G>C/c.859C>T in the 23-year-old man with LGMD2T-phenotype and c.79G>C homozygosity in the 74-year-old woman with CMS phenotype. WBMRI showed fatty degeneration of paraspinal, thigh adductor, and calf muscles in patient 1 and edematous changes of the soleus muscle in patient 2.
  
  
  
  This case of c.79G>C homozygosity causing a mild, late-onset CMS phenotype, confirms the mild nature of this common mutation. The descriptions of these 2 new GMPPB cases add to the knowledge regarding this recently discovered, heterogeneous disease. Muscle Nerve 56: 334-340, 2017.
authors.affiliation: Friedrich-Baur Institut, Department of Neurology, Ludwig-Maximilian University, Ziemssenstrasse 1a, 80336, Munich, Germany.
authors.forename: Federica
authors.initials: F
authors.lastname: Montagnese
authors.affiliation: Section of Diagnostic and Interventional Neuroradiology, Klinikum rechts der Isar, Technische Universität, Munich, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Klupp
authors.affiliation: Section of Diagnostic and Interventional Neuroradiology, Klinikum rechts der Isar, Technische Universität, Munich, Germany.
authors.forename: Dimitrios C
authors.initials: DC
authors.lastname: Karampinos
authors.affiliation: CeGaT GmbH, Tübingen, Germany.
authors.forename: Saskia
authors.initials: S
authors.lastname: Biskup
authors.affiliation: Genetikum, Neu-Ulm, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Gläser
authors.affiliation: Section of Diagnostic and Interventional Neuroradiology, Klinikum rechts der Isar, Technische Universität, Munich, Germany.
authors.forename: Jan S
authors.identifier: 0000-0002-7557-0003
authors.initials: JS
authors.lastname: Kirschke
authors.affiliation: Friedrich-Baur Institut, Department of Neurology, Ludwig-Maximilian University, Ziemssenstrasse 1a, 80336, Munich, Germany.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Schoser
mesh_terms: D000368:Aged; D006801:Humans; D049288:Muscular Dystrophies, Limb-Girdle / Q000150:complications / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D020294:Myasthenic Syndromes, Congenital / Q000235:genetics*; D009713:Nucleotidyltransferases / Q000235:genetics*; D010641:Phenotype; D055815:Young Adult
chemical_list: D009713:Nucleotidyltransferases; C026917:mannose 1-phosphate guanylyltransferase
keywords: GMPPB; LGMD2T; congenital muscular dystrophy; congenital myasthenic syndrome; dystroglycanopathy; limb-girdle muscular dystrophy