Adult polyglucosan body disease (APBD) is another kind of heritable glycogen storage disease (GSD) often associated with glycogen-branching enzyme (GBE) deficiency, which causes a neurodegenerative disorder due to an accumulation of abnormal polyglucosans in the cells of various body systems of humans and horses [18,19]. The gene discussed is GBE1; the disease is disorder of glycogen metabolism.