The glycogen storage diseases (GSD) are a group of autosomal recessive disorders of glycogen metabolism. Glycogen is the storage form of glucose in tissues. It is catabolised in the organism to glucose-1-phosphate if needed. GSD IIIa is a deficiency of glycogen debranching enzyme activity (GDE) which results in glycogen accumulation in liver and muscles. The clinical signs appear to be mild in the first year of life, becoming more prominent with age and leading to lethargy, exercise intolerance and episodic hypoglycemia with collapse.
Gregory, B.L., Shelton, G.D., Bali, D.S., Chen, Y.-T., and Fyfe, J.C. (2007). Glycogen storage disease type IIIa in curly-coated retrievers. J. Vet. Intern. Med. 21, 40–46.