Glycogen storage disease type 2B or Danon disease: A rare inherited biochemical disorder involving the harmful accumulation of certain chemicals (glycogen) in body tissues due to the deficiency of an enzyme (glucosidase or acid maltase) needed to break it down. Type IIB usually starts during childhood.
The list of signs and symptoms mentioned in various sources for Glycogen storage disease type 2B includes the 6 symptoms listed below:
- Proximal muscle weakness
- Thickening of heart muscle
- Mental retardation
- Intermittent hepatomegaly
- Glycogen deposits in the heart
Danon disease is caused by mutations in the LAMP2 gene. The LAMP2 gene provides instructions for making a protein called lysosomal associated membrane protein-2 (LAMP-2), which, as its name suggests, is found in the membrane of cellular structures called lysosomes. Lysosomes are compartments in the cell that digest and recycle materials. The role the LAMP-2 protein plays in the lysosome is unclear. Some researchers think the LAMP-2 protein may help transport cellular materials or digestive enzymes into the lysosome. The transport of cellular materials into lysosomes requires the formation of cellular structures called autophagic vacuoles (or autophagosomes), which then attach (fuse) to lysosomes. The LAMP-2 protein may be involved in the fusion between autophagic vacuoles and lysosomes.
Mutations in the LAMP2 gene lead to the production of very little or no LAMP-2 protein, which may impair the process of transporting cellular material into the lysosome. Some studies have shown that in cells without the LAMP-2 protein, fusion between autophagic vacuoles and lysosomes occurs more slowly, which may lead to the accumulation of autophagic vacuoles. People with Danon disease have an abnormally large number of autophagic vacuoles in their muscle cells. It is possible that this accumulation leads to breakdown of the muscle cells, causing the muscle weakness seen in Danon disease.
The phrase "signs of Glycogen storage disease type 2B" should, strictly speaking, refer only to those signs and symptoms of Glycogen storage disease type 2B that are not readily apparent to the patient. The word "symptoms of Glycogen storage disease type 2B" is the more general meaning; see symptoms of Glycogen storage disease type 2B. The signs and symptom information on this page attempts to provide a list of some possible signs and symptoms of Glycogen storage disease type 2B. This medical information about signs and symptoms for Glycogen storage disease type 2B has been gathered from various sources, may not be fully accurate, and may not be the full list of Glycogen storage disease type 2B signs or Glycogen storage disease type 2B symptoms. Furthermore, signs and symptoms of Glycogen storage disease type 2B may vary on an individual basis for each patient. Only your doctor can provide adequate diagnosis of any signs or symptoms and whether they are indeed Glycogen storage disease type 2B symptoms.