Glycogen storage disease type III

Glycogen storage disease type III is a genetic disorder, an inborn error of metabolism characterized by a deficiency in glycogen debranching enzymes. It is also known as Cori's disease in honor of the 1947 Nobel laureates Carl Cori and Gerty Cori. Other names include Forbes disease in honor of a clinician who further described the features of the disorder, or limit dextrinosis.^[1]

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Glycogen is a molecule the body uses to store carbohydrate energy. Symptoms of GSD-III are caused by a deficiency of the enzyme amylo-1,6 glucosidase, or debrancher enzyme. This causes excess amounts of an abnormal glycogen to be deposited in the liver, muscles and, in some cases, the heart.

GSD III is inherited in an autosomal recessive manner and occurs in about 1 of every 100,000 live births.

Presentation

Clinical manifestations are divided into four classes:

1. GSD IIIa, which clinically includes muscle and liver involvement ^[2]
2. GSD IIIb, which clinically has liver involvement but no muscle involvement
3. GSD IIIc and GSD IIId, which are rarer phenotypes with altered penetrance

The disease typically presents during infancy with hypoglycemia and failure to thrive. Clinical examination usually reveals hepatomegaly. Muscular disease, including hypotonia and cardiomyopathy usually occurs later.

The liver pathology typically regresses as patients enter adolescence, and few patients develop cirrhosis during adulthood.

Treatment

Treatment may involve a high protein diet, in order to facilitate gluconeogenesis.

References

1. ^ http://www.emedicine.com/ped/topic479.htm.
2. ^ Lucchiari S et al., Clinical and genetic variability of glycogen storage disease type IIIa: seven novel AGL gene mutations in the Mediterranean area. Am J Med Genet 2002 May 1;109(3):183-90.