Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ Key Features ++ Glycogen is a highly branched polymer of glucose that is stored in liver and muscle Different enzyme defects affect its biosynthesis and degradation Types 0, I, III, VI, and IX manifest with hypoglycemia in infants Types II, V, and VII manifest with rhabdomyolysis or muscle weakness Types IV and IX manifest with hepatic cirrhosis +++ Clinical Findings ++ Hepatic forms of the glycogenoses cause Growth failure Hepatomegaly Severe fasting hypoglycemia Glycogen synthase deficiency (GSD; glycogen storage disease type 0) Causes hypoglycemia, usually after about 12 hours of fasting Can cause mild postprandial hyperglycemia and hyperlactatemia Glycogenosis type IV, brancher enzyme deficiency, usually presents with progressive liver cirrhosis, as do some rare forms of phosphorylase kinase deficiency The gluconeogenesis disorder fructose-1,6-bisphosphatase deficiency presents with major lactic acidosis and delayed hypoglycemia on fasting Skeletal myopathy with weakness or rhabdomyolysis may be seen in Muscle phosphorylase deficiency (type V) Phosphofructokinase deficiency (type VII) Acid maltase deficiency (type II; Pompe disease) Infantile form of Pompe disease also has hypertrophic cardiomyopathy and macroglossia +++ Diagnosis ++ Initial tests include glucose, lactate, triglycerides, cholesterol, uric acid, transaminases, and creatine kinase Functional testing includes responsiveness of blood glucose and lactate to fasting An ischemic or nonischemic exercise test is helpful for myopathic forms Most glycogenoses can be diagnosed by molecular analysis Other diagnostic studies include enzyme assays of leukocytes, fibroblasts, liver, or muscle Disorders diagnosable from analysis of red blood cells include deficiency phosphorylase kinase (type IX) in half the cases Pompe disease can usually be diagnosed by assaying acid maltase in a blood spot with confirmation in fibroblasts +++ Treatment ++ Treatment is designed to prevent hypoglycemia and avoid secondary metabolite accumulations such as elevated lactate in glycogenosis type I In GSD1, the special diet must be strictly monitored with restriction of free sugars and measured amounts of uncooked cornstarch, which slowly releases glucose in the intestinal lumen Immunomodulation is used for patients whose treatment response declines due to antibodies to the recombinant enzyme Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth