The following points highlight the top ten types of glycogen storage diseases. The types are: 1. von Gierke’s Disease 2. Pompe’s Disease 3. Amylopectinosis 4. MC Ardle’s Disease 5. Galactosemia 6. Hereditary Fructose Intolerance 7. Lactosuria 8. Maltosuria 9. Fructosuria 10. Pentosuria.
Glycogen Storage Diseases: Type # 1. von Gierke’s Disease:
a. The disease is due to the deficiency of glucose-6-phosphatase for which glycogen cannot be broken down to liberate glucose and glucose-6-phosphate promotes glycogen synthesis.
b. Children with this disease tend to develop hypoglycemia.
c. They use fat mostly as an energy source and this leads to lipemia, acidemia and ketosis.
d. There is fatty infiltration of the liver.
e. The hypoglycemia inhibits insulin secretion which, in turn, also inhibits protein synthesis and growth is ceased.
f. Hypoglycemia stimulates epinephrine production which causes the breakdown of muscle glycogen forming lactate. This lactate competes with urate for excretion by the kidney. So blood urate level is increased.
Glycogen Storage Diseases: Type # 2. Pompe’s Disease:
a. The disease is due to the deficiency of a lysosomal enzyme, acid maltase.
b. There is excessive amount of glycogen in all tissues.
c. The heart is enlarged and there is extreme muscle weakness.
d. Death occurs usually before the ninth month of life.
Type III Glycogenosis (Limit Dextrinosis):
a. In this condition, there is an accumulation of limit dextrin in liver and muscles. This substance is produced by the action of phosphorylase on glycogen.
b. Debrancher enzyme system is deficient in this disease.
c. Patients with this disease are known to survive well into adult life.
Glycogen Storage Diseases: Type # 3. Amylopectinosis:
a. This disease is due to the deficiency of the branching enzyme in the liver.
b. Amylopectin’s are formed in the liver, heart, kidney and muscle.
c. The disease is fatal, survival being four years.
Glycogen Storage Diseases: Type # 4. MC Ardle’s Disease:
a. In this disease, there is a defect of muscle phosphorylase.
b. Cramp occurs in muscle after moderate exercise and recovery is attained during rest.
c. The exercised muscles can metabolize fructose.
Glycogen Storage Diseases: Type # 5. Galactosemia:
This is an inherited disorder in which there is high concentration of galactose in the blood. The incidence occurs in 1 in 18,000 births.
a. Galactose cannot be converted into glucose due to the deficiency of the enzyme galactose-1-℗-uridyl transferase. As a result, galactose and galactose-1-℗ accumulate in blood and tissues like liver, spleen, kidney, heart, lens of eye, cerebral cortex.
b. Galactose also accumulates in blood and tissues due to the minor type of galactokinase deficiency.
c. It is rarely claimed that galactose also accumulates in blood and tissues due to the deficiency of epimerase.
a. Infants become lethargic, fail to thrive, hypoglycemic due to non-conversion of galactose to glucose, may vomit and may suffer from jaundice.
b. Infants after two to three months may suffer from cirrhosis of liver, mental retardation, development of cataracts.
a. Increased blood galactose level.
b. Decreased blood sugar level.
c. Decreased inorganic phosphate level.
Glycogen Storage Diseases: Type # 6. Hereditary Fructose Intolerance:
a. This inherited disorder occurs due to the deficiency of the enzyme Aldolase B for which fructose-1 phosphate cannot be further metabolized.
b. Fructose administration in these patients leads to:
(i) Elevated level of fructose and fructose-1-℗ in blood.
(ii) Hypoglycemia accompanied by nausea, vomiting, and pro-fused sweating. This may be due to excessive insulin secretion.
(iii) Albuminuria, aminoaciduria.
This is a condition in which sugars are excreted in urine.
Glycogen Storage Diseases: Type # 7. Lactosuria:
Lactosuria occurs in women during the period of lactation. Small to moderate amounts of lactose may be found in the urine of most of the pregnant women, the amount increases as pregnancy advances. It appears more frequently in the afternoon.
Glycogen Storage Diseases: Type # 8. Maltosuria:
This is a rare condition of no known clinical significance.
Glycogen Storage Diseases: Type # 9. Fructosuria:
Fructose may appear in the urine under the following circumstances:
a. The patients with hepatic insufficiency excrete fructose in urine when large quantities of fructose are ingested.
b. Essential fructosuria is a rare congenital disorder in which there is the deficiency of fructokinase and characterized by inability to utilize fructose completely. Insulin has no influence upon this condition.
There are two varieties of this condition. In one, the metabolism of other carbohydrates is undisturbed and there are no clinical symptoms. In another form, the rise in blood fructose is accompanied by a sharp drop in the blood glucose concentration with severe symptoms of hypoglycemia.
This is due to the deficiency of aldolase B in the liver resulting in accumulation of fructose-1-phosphate which blocks important pathways of fructose utilization.
Glycogen Storage Diseases: Type # 10. Pentosuria:
Pentose may appear in the urine under the following circumstances:
a. After the ingestion of large quantities of fruits, there is alimentary pentosuria occurring in normal individuals. It has no clinical significance except the wrong idea for glycosuria.
b. Essential pentosuria is due to “inborn errors of metabolism”. This occurs owing to the lack of the enzyme L-xylitol dehydrogenase which causes the reduction of L-xylulose to xylitol in the liver. As a result, L-xylulose is excreted in urine. It occurs practically in males of Jewish subjects. The utilization of other carbohydrates is unimpaired.