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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 …
Contributors IC was involved in the clinical evaluation; design of the study; acquisition, analysis and interpretation of the data; and drafting of the manuscript. SP was involved in the design of the study; analysis and interpretation of the data; and drafting of the manuscript. ST was involved in the clinical evaluation; and acquisition, analysis and interpretation of the data. CMC, MS, GPC and MM were involved in the analysis and interpretation of the data; and revising of the manuscript. GF and PC were involved in the analysis and interpretation of the data. AB, FF and DV were involved in the acquisition of the data. FM was involved in the revising of the manuscript. SCP was involved in the clinical evaluation; acquisition of the data; and revising of the manuscript.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Foundation IRCCS Ca’ Granda Ospedale Maggiore Policlinico.
Provenance and peer review Not commissioned; externally peer reviewed.
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