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Glycogen Storage Disease

Common names or abbreviations:

	Glycogen storage disease
	glycogenoses

Description or definition:

Glycogen storage diseases are also called glycogenoses. The conditions are very rare and involve an inherited absence or deficiency of enzymes responsible for releasing glycogen as it is needed by the body during exercise and/or between meals. The body needs glucose in order to perform everyday functions. The stored form of glucose is called glycogen. When glucose is needed by the body, glycogen is released and broken down by an enzyme in the liver. With glycogen storage disease, glycogen is formed, but not released. Therefore, it continues to be stored in the liver, causing liver enlargement and other problems resulting from the body’s need for glucose.

The three glycogen storage diseases (GSD) most often reported in dogs are: Type I. GSD; Type II GSD, and Type III GSD.

Symptoms:

Types I and III GSD directly affect the liver. Clinical signs for both include muscle tremors, lack of coordination, retarded growth, hepatomegaly (abnormal enlargement of the liver), progressive abdominal distention as a result of hepatomegaly, hypoglycemia (low blood sugar), seizures, and weakness and depression due to hypoglycemia. Type I. GSD is most often seen in toy breed puppies, and symptoms are present between 6 and 12 weeks of age. Type III GSD is most often seen in German Shepherds and Akitas. Symptoms of muscular weakness and exercise intolerance has been noted at around 2 months of age. Type II. symptoms include progressive muscle weakness, frequent vomiting and regurgitation, megaesophagus (abnormal enlargement of the lower portion of the esophagus), dysphonia (hoaresness, difficulty in barking or vocalizing), persistent panting, cardiac abnormalities. The symptoms begin to appear at about 6 months of age, are progressive, and death usually occurs before two years of age.

Diagnosis:

Diagnosis can be made by a series of biopsies.

Treatment:

Many aspects of the GSD diseases are still poorly understood, and there are no cures. Treatment is aimed at alleviating symptoms through use of frequent small meals of high‑carbohydrate food, and administration of glucose therapy. Although sometimes the condition can be maintained through careful, and very controlled nutrition, unfortunately, the prognosis for many animals with GSD is poor and most succumb to these diseases at a young age.

Links to sites about this disease:

	http://www.ivis.org/special_books/Braund/braund18/chapter_frm.asp?LA=1
	http://www.upei.ca/~cidd/Diseases/nervous%20system%20disorders/lysosomal%20storage%20diseases.htm
	http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/25628.htm
	http://www.mesavet.com/library/gsd.htm

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Jessica in Arizona