Glycogen storage disease
Consisting of at least eight distinct errors of metabolism—all inherited—glycogen storage disease alters the synthesis or degradation of glycogen, the form in which glucose is stored in the body.
Normally, muscle and liver cells store glycogen. Muscle glycogen is used in muscle contraction; liver glycogen can be converted into free glucose, which can then diffuse out of the liver cells to increase blood glucose levels.
Glycogen storage disease manifests as a dysfunction of the liver, heart, or musculoskeletal system. Symptoms vary from mild and easily controlled hypoglycemia to severe organ involvement that may lead to cardiac and respiratory failure.
Causes
Almost all glycogen storage disease (types I through V and type VII) is transmitted as autosomal recessive traits. (See Types of glycogen storage disease.) The mode of transmission of type VI is unknown; type VIII may be an X-linked trait.
The most common type of glycogen storage disease is type I, glucose-6-phosphatase deficiency, or von
Gierke’s disease, which results from a deficiency of the liver enzyme glucose-6-phosphatase. It occurs in about 1 in 200,000 births, but the incidence may be higher in some populations. This enzyme converts glucose-6-phosphate into free glucose and is necessary for the release of stored glycogen and glucose into the bloodstream to relieve hypoglycemia.
Gierke’s disease, which results from a deficiency of the liver enzyme glucose-6-phosphatase. It occurs in about 1 in 200,000 births, but the incidence may be higher in some populations. This enzyme converts glucose-6-phosphate into free glucose and is necessary for the release of stored glycogen and glucose into the bloodstream to relieve hypoglycemia.
Types of glycogen storage disease
| Type | Deficiency | Inheritance Pattern |
|---|---|---|
| I (von Gierke’s) | Glucose-6-phosphatase | Autosomal recessive |
| II (Pompe’s) | Alpha 1,4-glucosidase (acid maltase) | Probably autosomal recessive in most patients (late onset may be autosomal dominant) |
| III (Cori’s) | Debranching enzyme (amylo-1,6-glucosidase) | Autosomal recessive |
| IV (Andersen’s) |
