Adult polyglucosan body disease (APBD) is an orphan disease and a glycogen storage disorder that is caused by an inborn error of metabolism. Symptoms can emerge any time after the age of 30; early symptoms include trouble controlling urination, trouble walking, and lack of sensation in the legs. People eventually develop dementia. A person inherits loss-of-function mutations in the GBE1 gene from each parent, and the lack of glycogen branching enzyme (the protein encoded by GBE1) leads to buildup of unbranched glycogen in cells, which harms neurons more than other kinds of cells.