Handbook of Genetic Counseling/Von Gierkes Disease (Glycogen Storage Disease Type I)

Von Gierkes Disease (Glycogen Storage Disease Type I) Description Pathway= The body needs sugar in the form of glucose to function. Glucose is what gives all of our cells the energy they need to function properly. In order to get it, it has to be broken down from larger molecules that store it (glycogen). It is primarily stored in the liver and muscles. This disorder has achnage in the genes that make the pieces that break down the larger molecules into sugar = the levels of sugar are too low and the large molecules start to build up. Deficiency in the breakdown of glucose. G6Pase activity requires 2 components of the microsomal membrane: (1) a glucose-6-phosphate specific transport system that shuttles G6P from the cytoplasm to the lumen of the endoplasmic reticulum (a G6P translocase), and (2) an enzyme, glucose-6-phosphate phosphohydrolase, bound to the luminal surface of the membrane. Three types GSD Ia = the basic defect in glucose-6-phosphatase activity ion the liver, kidney and intestinal lining. GSD Ib = defect is in the glucose-6-phosphate transfer gene so you can see activity of glucose-6-phosphatase when testing. GSD Ic = defect is in the pyrophosphate transfer - RARE GSD Id = defect in glucose transport - RARE Characteristics Type Ia (most commonly associated with vGD. Short stature & growth delay Abdomen protrusion Build up of glycogen and fat in the liver Enlarged liver and malignant/benign growths in the liver Yellow plaques on skin (xanthomas) Spider-like arteries, gout in the ear or kidney Bleeding disorders Hypoglycemia Hypertension Doll-like faces with large cheeks Type Ib All of the above Small numbers of neutrophils in the blood (neutropenia) Bacterial infections Oral and intestinal sores. Genetics Type Ia maps to chromosome 17q21. Type Ib maps to chromosome 11q23 All are autosomal recessive Diagnosis Based on variety of lab results G6PD Increase in lipids in blood (lipidemia) High levels of uric acid in blood (hyperurcemia) High levels of ketones in blood (ketonemia) Metabolic acidosis (increase of acids or decrease in water fluid) Treatment Glucose drinks during the day Infusion at night through a nasogastric tube Cornstarch throughout the day for older children Dietary restrictions on fructose and galactose = need to supplement with calcium and multivitamins. Add Allopurinol to reduce uric acid levels which occurs because of the decrease in renal clearance and the increased production of uric acid as glycogen is not broken down. Notes The information in this outline was last updated in 2000.