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Glycogen Storage Diseases
Carbohydrate metabolism provides energy for metabolic functions of cell. Metabolism of glucose generates ATP by glycolysis and oxidative phosphorylation. Any one of several heritable diseases characterized by the abnormal storage and accumulation of glycogen in the tissues, esp. in the liver
Dietary sources of glucose:
- · Polysaccharide (starch)
- · Disacchride (lactose, maltose, sucrose)
- ·Monosaccharide (galactose, fructose).
- Sucrose is fructose + glucose.
- Lactose is galactose + glucose.
- Fructose is found in fruits, vegetables, honey.
- Galactose is found in milk. Glycogen is storage form of glucose in liver and muscles.
Defects in glycogen metabolism result in accumulation of glycogef, in tissues called glycogen storage diseases.
Most common GSDs are:
| Type | Enzyme | Percent of total |
| Liver glycogenoses | ||
| Type I | Glucose-6-phosphatase system, This autosomal recessive genetic disorder is due to a glucose-6-phosphatase deficiency. | 25 |
| Type III | Glycogen debrancher, disease caused by a deficiency of two debranching enzymes in liver and muscle tissues. | 24 |
| Type VI and VIII | Liver phosphorylase and phosphorylase b kinase | 30 |
| Type IV | Glycogen branching enzyme, disease marked by liver failure, muscular weakness, muscular contractures, and death in the first few years of life | 3 |
| Muscle glycogenoses | ||
| Type II | Acid maltase, disease caused by a deficiency of lysosomal -glucosidase. | 15 |
| Type V | Muscle phosphorylase, disease caused by a muscle phosphorylase deficiency | 2 |
| Type VII | Phosphofructokinase, disease caused by a deficiency of muscle phosphofructokinase and characterized by muscular weakness and cramping following exercise | <1 |
- · Glucose-6 phosphate deficiency
- · Lysosomal acid alpha glucosidase deficiency
- · Myophosphorylase deficiency – Mc Ardle disease.
Glucose-6 phosphatase deficiency (von Gierke disease) or GSD-I
- · It is an autosomal recessive disorder that causes glucose – 6 – phosphatase deficiency in liver, kidney and intestinal mucosa.
- · Age of presentation is in neonates or infants.
- · There is hepatomegaly, but liver enzymes are usually normal.
- · Lactic acidosis.
- · Doll-like face, fat cheeks, short stature, protuberant abdomen.
- · Kidneys are enlarged and there may be kidney stones.
- · Hyperuricemia, hyperlipidemia and hypoglycemia.
- · Epistaxis is common.
- · Polycystic ovaries without polycystic ovarian syndrome (no acne or hirsutism).
- · Proteinuria.
Treatment
- Blood sugar level should be maintained Starch is given
- Fructose and galactose is avoided Multivitamins
- Calcium
- Allopurinol
- HMG – CoA reductase inhibitors (Statins) ACE inhibitors.
Pompe disease or GSD II
- · There is deficiency of lysosomal acid maltas.
- · There is skeletal myopathy and cardiomyopathy.
- · Serum creatinine kinase and LDH are increased.
Treatment
- High protein diet
- Enzyme replacement therapy.
Mc Ardle disease or GSD-V
- · There is muscle phosphorylase deficiency
- · Presents in adults
- · There is exercise intolerance
- · Muscle cramps
- · Burgandy coloured urine (red urine) – due to rhabdomyolysis
- · There is inflammatory myopathy.
Treatment
- High protein diet.