## Most Common Glycogen Storage Disorder **Key Point:** Type I glycogen storage disease (Von Gierke disease) is the most common symptomatic glycogen storage disorder, accounting for approximately 25% of all GSDs. ### Clinical Features of Type I GSD | Feature | Type I (GSD-I) | |---------|----------------| | Enzyme defect | Glucose-6-phosphatase | | Glycogen structure | Normal | | Age of onset | 3–4 months | | Hepatomegaly | Severe (can reach pelvis) | | Fasting hypoglycemia | Severe, < 40 mg/dL | | Lactic acidosis | Present | | Hyperuricemia | Present (gout risk) | | Growth | Severely stunted | | Muscle weakness | Minimal (muscles spared) | **High-Yield:** Type I causes the most severe fasting hypoglycemia because glucose-6-phosphatase is the final enzyme in both gluconeogenesis and glycogenolysis — without it, the liver cannot release free glucose into the bloodstream. ### Why Type I is Most Common 1. **Incidence:** 1 in 100,000 births (highest among all GSDs) 2. **Severe presentation:** Diagnosed early due to symptomatic hypoglycemia in infancy 3. **Requires lifelong management:** Frequent feeds, cornstarch, strict dietary control ### Comparison with Other Common GSDs | Type | Enzyme | Frequency | Key Finding | |------|--------|-----------|-------------| | I | Glucose-6-phosphatase | Most common | Severe fasting hypoglycemia | | II | Acid maltase | 2nd most common | Cardiomegaly, muscle weakness | | III | Debranching enzyme | 3rd most common | Milder than Type I | | IV | Branching enzyme | Rare | Abnormal glycogen structure | **Clinical Pearl:** Type I patients often have a characteristic "doll-like" facies with fat cheeks and short stature, and are at high risk for hepatic adenomas and renal disease in adulthood. **Mnemonic:** **GLUT** for Type I — **G**lucose-6-phosphatase, **L**iver (severe hepatomegaly), **U**ric acid (hyperuricemia), **T**reatment (frequent feeds).
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.