A. Classification by Symptoms

1. Hepatic-Hypoglycemic Effects
   1. Type Ia - von Gierke. Glucose 6-Phosphatase deficiency
   2. Type Ib - Glucose 6-phosphate Microsomal Translocase deficiency
   3. Type III - Cori Disease. Glycogen Debrancher enzyme deficiency
   4. Type VI - Hers Disease. Hepatic Phosphorylase (HP) or HP b Kinase deficiency
2. Muscle Problems
   1. Type V - McArdle Disease: muscle phosphorylase deficiency; pain, cramps, myoglobinuria
   2. Type VII - phosphofructokinase deficiency; similar symptoms to Type V
3. Other
   1. Type II - Pompe Disease. Lysosomal alpha-1,4-glucosidase deficiency
   2. Type IV - Brancher Enzyme deficiency

B. Von Gierke Disease

1. Hypoglycemia, hepatomegaly, coagulopathy (bleeding), short stature
2. Hepatic adenomas and renal enlargement can occur
3. Uric acid, triglyceride and lactate are increased
4. Autosomal recessive

C. Cori Disease

1. Symptoms similar to von Gierke Disease
2. Increased cholesterol, triglyceride,
3. Elevation in hepatic transaminases (AST, ALT) - rarely progresses to hepatic fibrosis
4. Frequent feedings required

D. McArdle Disease [2]

1. Most common disorder of muscle carbohydrate metabolism
2. Prevalence of ~1 per 100,000
3. Autosomal recessive error of metabolism
   1. Caused by mutations in myophosphorylase
   2. Completely prevents breakdown of glycogen in muscle
4. Male predominance; usually diagnosed in adulthood
5. Pain, cramps, myoglobinuria on strenous exercise
6. Muscle destruction with creatinine kinase elevation in blood
7. "Second wind" occurs after 10 minutes of strenuous exercise
   1. This is due to increased delivery of extramuscular energy to muscle
   2. Main source of this energy is glucose
   3. Intravenous glucose bypasses metabolic block in McArdle disease
   4. Oral glucose does not greatly improve exercise
8. Avoidance of strenuous exercise is main treatment
9. Oral sucrose improves exercise / work performance in early stages of exercise

E. Other Disorders [3]

1. Danon Disease
   1. X-linked lysosome-associated membrane protein 2 (LAMP2) deficiency
   2. Usually cause multisystem glycogen storage disease
   3. May also cause primary cardiomyopathy
2. AMP-Activated Protein Kinase Gamma2 (PRKAG2) Deficiency
   1. Accumulation of cardiac glycogen and hypertrophic cardiomyopathy
   2. Ventricular pre-excitation is common

References

1. Fernandes J. 1995. Eur J Pediatr. 154(6):423
2. Vissing J and Haller RG. 2003. NEJM. 349(26):2503
3. Arab M, Maron BJ, Gorham JM, et al. 2005. NEJM. 352(4):362