glycogen disorders Flashcards
What are Glycogen Storage Diseases (GSDs)?
A group of metabolic disorders caused by enzyme defects affecting glycogen synthesis or breakdown.
What is Von Gierke’s Disease (GSD Type I)?
Deficiency of glucose-6-phosphatase, leading to severe fasting hypoglycemia, hepatomegaly, and lactic acidosis.
Why does Von Gierke’s disease cause hypoglycemia?
Liver cannot release free glucose due to defective glucose-6-phosphatase.
What is Pompe’s Disease (GSD Type II)?
Deficiency of lysosomal α-1,4-glucosidase (acid maltase), leading to glycogen accumulation in lysosomes.
What are the clinical features of Pompe’s disease?
Cardiomegaly, muscle weakness, and early death in infantile form due to heart failure.
What is Cori’s Disease (GSD Type III)?
Deficiency of debranching enzyme (α-1,6-glucosidase), causing accumulation of limit dextrins.
How does Cori’s disease differ from Von Gierke’s?
Cori’s disease has milder hypoglycemia and no lactic acidosis because gluconeogenesis remains intact.
What is Anderson’s Disease (Amylopectinosis, GSD Type IV)?
Deficiency of branching enzyme, causing glycogen to have long, unbranched chains that precipitate in the liver.
What are the clinical features of Anderson’s disease?
Hepatosplenomegaly, cirrhosis, failure to thrive, and early childhood death due to liver failure.
What is McArdle’s Disease (GSD Type V)?
Deficiency of muscle glycogen phosphorylase, causing muscle cramps, myoglobinuria, and exercise intolerance.
Why does McArdle’s disease cause second-wind phenomenon?
After a brief period of rest, alternative energy sources (fatty acids) become available, improving exercise tolerance.
What is Hers’ Disease (GSD Type VI)?
Deficiency of liver glycogen phosphorylase, causing mild hypoglycemia and hepatomegaly.
What is Tarui’s Disease (GSD Type VII)?
Deficiency of phosphofructokinase (PFK-1) in muscle and RBCs, leading to exercise intolerance and hemolysis.
