Definition:

Glycogen storage diseases (GSD) are inherited metabolic disorders of glycogen metabolism. They are divided into types 0 to XV, according to enzyme or transporter deficiency and organ distribution. The hepatic GSDs lead to hepatomegaly and hypoglycemia due to the lack of distribution of glucose to the organism. 80% of hepatic GSD is formed by types I, III, and IX. GSD I involves the liver, kidney and intestine, and the clinical manifestations are hepatomegaly, failure to thrive, hypoglycemia, hyperlactatemia, hyperuricemia and hyperlipidemia. GSD IIIa patients display symptoms and signs due to the enzyme deficiency in liver, skeletal muscle and heart, whereas the remaining patients with GSD IIIb have only liver-related phenotypes. GSD IV usually presents in the first year of life, with hepatomegaly and growth retardation. GSD VI and IX are caused by a deficiency of the liver phosphorylase and phosphorylase kinase system, and with usually moderate symptoms which manifest mainly in childhood.