GYG1 and skeletal muscle disorder: Glycogenin-1-associated disorders include GSD XV, manifesting as a pure cardiomyopathy with myocardial polyglucosan bodies with a non-functional glycogenin-1, and polyglucosan body myopathy 2 (PGBM2), presenting with a pure skeletal myopathy with variable distribution of muscular weakness, with a limb-girdle phenotype or distal myopathy [64].