We recently identified polyglucosan body myopathy-2, a pure skeletal myopathic form of glycogen storage disease type XV, caused by glycogenin-1 deficiency, the primingenzyme of glycogen synthesis. To date 22 patients have been reported. They have juvenile to late-onset clinical symptoms with a variable distribution of muscle weakness. Muscle biopsies show the accumulation of polyglucosan bodies, consisting of hyper-intense periodic acid-Schiff (PAS)-positive material with a variable resistance to alpha-amylase treatment. Although cardiac involvement has been reported in 4 patients with glycogenin-1 gene (GYG1) mutations, these patients did not show any clear evidence of skeletal muscle disease. Here, we describe a 63-year-old woman born to consanguineous French parents, who developed right shoulder pain, difficulty climbing stairs and left foot weakness causing stumbling episodes at 46 years of age. Over time, the patient reported increasing difficulty elevating the right arm. At 61 years of age she also developed slight difficulty with left shoulder movement, and more recently she reported rare forearm fasciculations and nocturnal cramps in her thighs, calves, and toes.