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Longitudinal follow-up and muscle MRI pattern of two siblings with polyglucosan body myopathy due to glycogenin-1 mutation
  1. Irene Colombo1,
  2. Serena Pagliarani2,
  3. Silvia Testolin1,
  4. Claudia Maria Cinnante3,
  5. Gigliola Fagiolari1,
  6. Patrizia Ciscato1,
  7. Andreina Bordoni2,
  8. Francesco Fortunato2,
  9. Francesca Magri2,
  10. Stefano Carlo Previtali4,
  11. Daniele Velardo4,
  12. Monica Sciacco1,
  13. Giacomo Pietro Comi2,
  14. Maurizio Moggio1
  1. 1 Neuromuscular and Rare Disease Unit, Department of Neuroscience, Foundation IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
  2. 2 Department of Pathophysiology and Transplantation Neuroscience Section (DEPT), Neurology Unit, Dino Ferrari Centre, Foundation IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
  3. 3 Unit of Neuroradiology, Department of Neuroscience, Foundation IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
  4. 4 Division of Neuroscience and Department of Neurology, Institute of Experimental Neurology (INSPE), IRCCS San Raffaele Scientific Institute, Milan, Italy
  1. Correspondence to Dr Irene Colombo, Neuromuscular and Rare Disease Unit, Department of Neuroscience, Foundation IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Via F Sforza 35, Milano 20122, Italy; irene_colombo{at}libero.it IC and SP contributed equally to this manuscript.

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Polyglucosan bodies (PBs) are deposits of amylopectin-like polysaccharides, detected in muscles of patients affected with glycogenoses-like branching enzyme (GBE) and phosphofructokinase deficiencies.1

Recently, mutations in RBCK1 have been associated with a skeletal PBs myopathy,2 as well as mutations in GYG1, encoding for glycogenyn-1.3 All these conditions have autosomal recessive inheritance. Only seven unrelated cases with mutations in GYG1 have been reported, characterised by variable age at onset (from childhood to 7th decade), mainly proximal weakness, normal creatine kinases (CKs) levels and myopathic electromyography (EMG).3

We have been, for the past 35 years, following two affected sisters now aged 71 and 64 years (P.IV-5 and P.IV-10) (see online supplementary figure S1A). Their parents were both healthy first cousins from a little village in the Italian Alps. Both sisters had normal motor development.

At the age of 30 years, P.IV-5 showed weakness in arm abduction, more prominent on the right side. The disease course was slowly progressive over the decades, with early involvement of proximal limb muscles. Waddling gait with hyperlordosis was first observed when she was in her late 40s. She started to use a wheelchair outdoors at the age of 59 years. In the following years she became completely a wheelchair user and dependent for her daily activities. Her last examination, at the age of 71 years, showed facial weakness, which was initially absent, with muscle atrophy and hypotonia, absent deep tendon reflexes (DTR) and severely compromised muscle power (Medical Research Council (MRC) score: neck flexors 3, neck extensors 2, shoulder abductors 0, forearm extensors/flexors 0, wrist extensors 0, wrist flexors and hand grip 2, hip flexors/extensors 0, thigh extensors/flexors 2, foot plantar flexors and …

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