Biomarker for Glycogen Storage Diseases - AN INTERNATIONAL, MULTICENTER, EPIDEMIOLOGICAL PROTOCOL

Glycogen storage diseases (GSDs) are a group of inherited genetic disorders that cause glycogen to be improperly stored in the body. People with glycogen storage diseases have a buildup of abnormal amounts or types of glycogen in their tissues.

The main types of glycogen storage diseases are categorized by number and name. They include:

People with GSD I may have episodes of low blood sugar (hypoglycemia), usually during periods of fasting, due to the ability to store glycogen but inability to properly release it. People with GSD I typically develop an enlarged liver (hepatomegaly) from the storage of glycogen. Elevations in liver function enzymes, blood fat and cholesterol levels, lactic acid, and uric acid also occur. Additional features of GSD I can include decreased bone density, poor growth, kidney disease, liver adenomas, and delayed puberty. Treatment primarily consists of dietary management to maintain normal blood glucose levels and prevent hypoglycemia. GSD I is further divided into subtypes. GSD Type Ia is caused by a deficiency of glucose-6-phosphatase (G6Pase) primarily in the liver, and GSD Type Ib is caused by a deficiency of glucose-6-phosphate translocase. Many of the symptoms are similar, especially early in life. However, some people with Type Ib are more prone to infections given a weaker immune system. GSD I is caused by a non-working change in either the G6PC gene or the SLC37A4 gene, causing the deficiency of the particular enzyme. GSD I follows autosomal recessive inheritance.

Glycogen Storage Disease Type II [also known as Pompe disease, Acid Maltase Deficiency, Glycogenosis Type II, Acid alpha-Glucosidase Deficiency, Lysosomal alpha-Glucosidase Deficiency] Pompe disease is an inherited and often fatal disorder caused by the deficiency of acid alpha-glucosidase (GAA), an enzyme needed to breakdown glycogen (sugar that is stored for energy) in specialized structures in the body, called lysosomes. Patients with Pompe disease have little or no GAA enzyme activity and cannot breakdown glycogen. The excess glycogen accumulates and is stored in the heart, skeletal muscle and other tissues, causing the progressive symptoms of Pompe disease.Glycogen Storage Disease Type III [also known as Cori disease, Forbes disease, Debrancher enzyme deficiency, Limit Dextrinosis]