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What is Adult polyglucosan body disease and explain in detail?
Adult polyglucosan body disease (APBD) is a rare genetic glycogen storage disorder 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.
Most people first go to the doctor due to trouble with urination.  The condition is diagnosed by gathering symptoms, a neurological examination, laboratory tests including genetic testing, and medical imaging.  As of 2015 there was no cure or treatment, but the symptoms could be managed.  People diagnosed with APBD can live a long time after diagnosis, but will probably die earlier than people without the condition.

Signs and symptoms
Adult polyglucosan body disease is a condition that affects the nervous system. People with this condition have problems walking due to reduced sensation in their legs (peripheral neuropathy) and progressive muscle weakness and stiffness (spasticity). Damage to the nerves that control bladder function (neurogenic bladder) causes progressive difficulty in controlling the flow of urine. About half of people with adult polyglucosan body disease experience dementia.  Most people with the condition first complain of bladder issues.People with adult polyglucosan body disease typically first experience signs and symptoms related to the condition between ages 30 and 60.

Causes
APBD is an autosomal recessive disorder that is caused when a person inherits genes from both parents containing one or more loss-of-function mutations in the gene GBE1 which encodes for glycogen branching enzyme, also called 1,4-alpha-glucan-branching enzyme.

Mechanism
The GBE1 gene provides instructions for making the glycogen branching enzyme. This enzyme is involved in the production of a complex sugar called glycogen, which is a major source of stored energy in the body. Most GBE1 gene mutations result in a shortage (deficiency) of the glycogen branching enzyme, which leads to the production of abnormal glycogen molecules. These abnormal glycogen molecules, called polyglucosan bodies, accumulate within cells and cause damage. Neurons appear to be particularly vulnerable to the accumulation of polyglucosan bodies in people with this disorder, leading to impaired neuronal function.Some mutations in the GBE1 gene that cause adult polyglucosan body disease do not result in a shortage of glycogen branching enzyme. In people with these mutations, the activity of this enzyme is normal. How mutations cause the disease in these individuals is unclear. Other people with adult polyglucosan body disease do not have identified mutations in the GBE1 gene