A table summarizing the main glycogen storage diseases (GSDs) with enzyme defects, key clinical features, and mnemonics to aid memorization:
| Glycogen Storage Disease | Enzyme Defect | Key Clinical Features | Mnemonic |
| Type I: von Gierke Disease (GSD I) | Glucose-6-phosphatase | Severe fasting hypoglycemia, hepatomegaly, lactic acidosis, hyperlipidemia, hyperuricemia | “von Gierke: ‘G6P’s Gone, Liver Left Low” |
| Type II: Pompe Disease (GSD II) | Acid maltase (α-1,4-glucosidase) | Cardiomegaly, hypotonia, muscle weakness, glycogen buildup in lysosomes (infantile form often fatal) | “Pompe Packs Glycogen in the Pump (heart)” |
| Type III: Cori Disease (GSD III) | Debranching enzyme | Hepatomegaly, mild hypoglycemia, muscle weakness, glycogen with short outer branches | “Cori Can’t Clear Chains” |
| Type IV: Andersen Disease (GSD IV) | Branching enzyme | Hepatomegaly, cirrhosis, failure to thrive, abnormal glycogen with few branch points | “Andersen’s Absent Arms (glycogen branches)” |
| Type V: McArdle Disease (GSD V) | Muscle phosphorylase | Exercise intolerance, muscle cramps, myoglobinuria, “second-wind” phenomenon | “McArdle’s Muscles (need) More” |
| Type VI: Hers Disease (GSD VI) | Liver phosphorylase | Mild hypoglycemia, hepatomegaly, growth delay, generally mild disease course | “Hers’ hypoglycemia is mild” |
| Type VII: Tarui Disease (GSD VII) | Phosphofructokinase (PFK-1) | Exercise intolerance, muscle cramps, myoglobinuria, hemolysis | “Tarui tires easily” |
| Type IX: Phosphorylase Kinase Deficiency (GSD IX) | Phosphorylase kinase | Hepatomegaly, mild hypoglycemia, growth delay | “Phosphorylase Kinase, kinder symptoms” |
Explanation of Mnemonics:
- von Gierke: ‘G6P’s Gone, Liver Left Low: Highlights the deficiency in glucose-6-phosphatase and hypoglycemia.
- Pompe Packs Glycogen in the Pump (heart): Emphasizes glycogen buildup affecting the heart in Pompe disease.
- Cori Can’t Clear Chains: Reflects the incomplete breakdown of glycogen branches, causing short outer chains.
- Andersen’s Absent Arms: Refers to the abnormal structure of glycogen with few branches.
- McArdle’s Muscles (need) More: Highlights the energy deficiency in muscles during exercise due to glycogen buildup.
- Hers’ hypoglycemia is mild: Hers disease has mild hypoglycemia due to liver phosphorylase deficiency.
- Tarui tires easily: Reflects exercise intolerance due to impaired phosphofructokinase activity.
- Phosphorylase Kinase, kinder symptoms: Type IX has generally milder symptoms due to partial liver phosphorylase activation issues.
