Glycogen Storage Diseases

Question 1

Findings: McArdle disease (type V)

Answer 1

Increased glycogen in muscle that cannot be broken down

Upon exercise:

1. Painful muscle cramps
2. Myoglobinuria (red urine)
3. Usually normal glucose, lactate
4. Arrhythmia (electrolyte abnormalities)
5. Second-wind phenomenon during exercise

Question 2

Findings: Von Gierke disease (type I)

Answer 2

1. Severe fasting hypoglycemia → lethargy, seizures
2. Increased glycogen in liver
3. Increased blood lactate (Cori cycle disrupted)
4. Increased TGs
5. Increased uric acid (gout)
6. Hepatomegaly

Question 3

Findings: Cori disease (type III)

Answer 3

Milder form of Von Gierke (type I) but with normal blood lactate levels (gluconeogenesis intact)

Accumulation in liver AND muscle:

1. Hypotonia/weakness (vs von Gierke)
2. Hepatomegaly
3. Accumulation of limit dextrin-like structures in cytosol

Question 4

Deficient enzyme: McArdle disease (type V)

Answer 4

Skeletal muscle glycogen phosphorylase

Question 5

Deficient enzyme: Pompe disease (type II)

Answer 5

Lysosomal acid alpha-1,4-glucosidase

(acid maltase)

Alpha-1,6-glucosidase activity

Question 6

Microscopy of Pompe disease (type II)

Answer 6

Electron rich granules inside lysosomes

Question 7

Deficient enzyme: Von Gierke disease (type I)

Answer 7

Glucose-6-phosphtase

Question 8

Treatment: Von Gierke disease (type I)

Answer 8

Frequent oral glucose/cornstarch

Avoid: Fructose, galactose, sucrose, lactose

Question 9

Findings: Pompe disease (type II)

Answer 9

1. Cardiomegaly
2. HCM
3. Macroglossia
4. Hypotonia
5. Exercise intolerance
6. Systemic findings lead to early death
7. Hepatomegaly (from heart failure)

Question 10

Treatment: McArdle disease

Answer 10

Supplement simple sugars before physical activity

Question 11

Deficient enzyme: Cori disease (type III)

Answer 11

Alpha-1,6-glucosidase (debranching enzyme)