First, when there is low activity of the branching enzyme, newly formed glycogen is manufactured incorrectly into long strands called “polyglucosan bodies.” These polyglucosan bodies cannot be used for fuel, so they build up inside nerve cells. This causes damage to these nerves. The damage often results in numbness and eventually weakness in the muscles controlled by these nerves. Hence, this disorder has become known as “Adult Polyglucosan Body Disease.”
Second, since a lot of the glycogen was built wrong and cannot be used as normal fuel, the cells needing this fuel run low on energy much faster than normal. As a result, patients with APBD often report serious fatigue at certain times during the day.