Health Information

Abnormal amounts of glycogen are deposited in various diseases due to inherited deficiencies of the enzymes involved in glycogen metabolism. In addition to this they produce deleterious effects on the growth and well being of the individual. The details of different types of glycogen storage diseases are given below:

Von Gierke’s disease:

Edger Von Gierke described the first glycogen storage disease in 1929. Coris elucidated in 1952 the enzymes deficiency that caused the disease. This disease is due to the absence of enzyme, glucose 6 phosphatase in liver and intestinal mucosa. Due to this, liver cells, intestinal mucosa and renal tubular epithelial cells are loaded with glycogen, which is normal in structure but unavailable metabolically.

Clinical and biochemical features of Von Gierke’s disease:

1. The absence of glucose 6-phosphatase in liver leads to hypoglycemia since liver is not able to convert glucose 6-PO4 into free glucose. The phosphorylated sugar does not leave the liver due to membrane impermeability.
2. There is a compensatory increase in glycolysis in the liver, leading to a high level o f lactate and pyruvate in the blood. Increased blood lactate competes with uric acid excretion by kidneys. This results in increased retention of uric acid in blood and the children suffering from this disease may develop symptoms of gout.
3. Due to limited availability of free glucose, most tissues except liver use fat as energy source, which leads to lipaemia and ketoacidosis.
4. Excess of acetyl CoA production by increased glycolysis in the liver leads to increased fatty acid synthesis, which may lead to the formation of fatty liver.
5. Hypoglycemia inhibits insulin secretion, which, in turn, affects protein synthesis and causes stunted growth (dwarfism).
6. Hypoglycemia induces secretion of glucagons, which causes breakdown of muscle glycogen, producing high levels of lactate and lactic acidosis.

Pompe’s disease:

The enzyme defect in Pompe’s disease is the absence of Lysosomal alpha glucosidases. All organs including liver and muscle are affected due to massive accumulation of normal glycogen. Enlargement of heart (cardiomegaly) is commonly seen. Muscle hypotension leads to muscle weakness. In most cases, cardio respiratory failure produces death before the age two.