- At least 15 types have been identified, all resulting in abnormal glycogen metabolism and the accumulation of glycogen within cells.
- Periodic acid–Schiff stain identifies glycogen and is useful in identifying these diseases.
- Very Poor Carbohydrate Metabolism.
- Types I, II, III, and V are autosomal recessive.
| Von Gierke disease (type I) | Severe fasting hypoglycemia, ↑↑ Glycogen in liver and kidneys, ↑ blood lactate, ↑ triglycerides, ↑ uric acid (Gout), and hepatomegaly, renomegaly. Liver does not regulate blood glucose. | Glucose-6-phosphatase | Treatment: frequent oral
glucose/cornstarch; avoidance of fructose and galactose Impaired gluconeogenesis and glycogenolysis |
| Pompe disease (type II) | Cardiomegaly, hypertrophic cardiomyopathy, hypotonia, exercise intolerance, and systemic findings lead to early death. | Lysosomal acid α-1,4-glucosidase with α-1,6-glucosidase activity (acid maltase) | PomPe trashes the PumP (1,4) (heart, liver, and muscle) |
| Cori disease (type III) | Milder form of von Gierke (type I) with normal blood lactate levels. Accumulation of limit dextrin–like structures in cytosol. | Debranching enzyme (α-1,6-glucosidase) | Gluconeogenesis is intact |
| McArdle disease (type V) | ↑ glycogen in muscle, but muscle cannot break it down → painful Muscle cramps, Myoglobinuria (red urine) with strenuous exercise, and arrhythmia from electrolyte abnormalities. Second-wind phenomenon noted during exercise due to ↑ muscular blood flow.
(Myophosphorylase) |
Skeletal muscle glycogen phosphorylase
Hallmark is a flat venous lactate curve with normal rise in ammonia levels during exercise
|
Blood glucose levels typically unaffected
McArdle = Muscle |