Glycogen Storage Diseases

Question 1

Type I: 
Name? 
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 1

• Name: Von Gierke’s Disease
• Enzyme: Glucose-6-phosphatase (enzyme or translocase)
• Organs: Liver + kidney (NOT muscle)
• Glycogen: increased (can’t utilize glycogen); normal structure
• Features: Enlarged liver, gouty arthritis, failure to thrive, severe hypoglycemia, increased lactate, hyperuricemia, hyperlipidemia, developmental disability

Question 2

Type II: 
Name? 
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 2

• Name: Pompe’s Disease
• Enzyme: 1,4-glucosidase (lysosomal)
• Organs: All
• Glycogen: Massive increase (accumulates in lysosome); normal structure
• Features: Cardiorespiratory failure, cardiomegaly, hypotonia, death (usually before age 2)

Question 3

Type III:
Name?
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 3

• Name: Cori’s disease
• Enzyme: Amylo-1,6-debranching enzyme
• Organs: *Muscle + liver
• Glycogen: Increased (can’t debranch); short outer (1,4-glucosidase still works)
• Features: Mild version of Von Gierke’s- enlarged liver, gouty arthritis, failure to thrive, severe hypoglycemia, increased lactate, hyperuricemia, hyperlipidemia, developmental disability

Question 4

Type IV:
Name?
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 4

• Name: Anderson’s Disease
• Enzyme: Branching enzyme
• Organs: Liver + spleen (unique)
• Glycogen: Normal amount; long branches (glycogen not formed properly)
• Features: Progressive cirrhosis, death (usually before age 2)

Question 5

Type V:
Name?
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 5

• Name: McArdle’s Disease
• Enzyme: Myophosphorylase (alpha-1,4)
• Organs: *Muscle
• Glycogen: Moderate amount (can partially compensate w/ liver glycogen stores); normal structure
• Features: (like Tarui’s Disease)- Limited ability to perform strenuous exercise, painful muscle cramps.

Question 6

Type VI:
Name?
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 6

• Name: Hers’ Disease
• Enzyme: Glycogen phosphorylase
• Organs: Liver
• Glycogen: Increased amount (can’t break down glycogen)
• Features: Similar to Cori’s (mild version of Von Gierke’s)- enlarged liver, gouty arthritis, failure to thrive, severe hypoglycemia, increased lactate, hyperuricemia, hyperlipidemia, developmental disability

Question 7

Type VII:
Name?
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 7

• Name: Tarui’s Disease
• Enzyme: Muscle PFK-1
• Organs: *Muscle
• Glycogen: Increased amount (glucose builds up and is stored)
• Features: (like McArdle’s dz)- Limited ability to perform strenuous exercise, painful muscle cramps.

Question 8

Type VIII. (no name)
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 8

• Enzyme: Phosphorylase kinase
• Organs: Liver
• Glycogen: Increased amount (can’t activate the phosphorylase to break down glycogen); normal
• Features: Mild liver enlargement, mild hypoglycemia

Question 9

Type 0. (no name)
Defective enzyme?
Affected organ(s)?
Affect on glycogen?
Clinical features?

Answer 9

• Glycogen synthase (alpha-1,4)
• Liver
• Decreased (can’t synthesize glycogen)
• Hypoglycemia, postprandial lactic acidemia, fasting ketosis

Question 10

Define hyperlipidemia.

What are its sx?

Answer 10

Hyperlipidemia: high fasting levels of fatty acids in the blood 
Sx: - Poor growth
- Muscle cramps
- Low blood sugar
- A greatly enlarged liver
- A swollen belly
- Abnormal blood test

Question 11

What is the typical treatment for management of GSD’s?

Answer 11

Frequent high carb meals during the day, cornstarch, continuous nighttime feeding and medicine.