Several different types of glycogen-storage disease have been identified in dogs

Glycogen-storage diseases are caused by an enzyme deficiency that prevents normal glycogen metabolism. The effect is hypoglycaemia because the affected individual is unable to mobilise glucose from glycogen stores. Glucose is required as an obligatory energy source for the normal function of the following tissues  :

• Blood cells
• Renal medullary cells
• Nervous tissue (especially the brain)
• Fast-twitch muscle fibres use glucose as an energy source. These are the predominant fibres in fast sped

The clinical signs of hypoglycaemia include :

• Muscle weakness
• Exercise intolerance
• Fatigue
• Collapse
• Ataxia
• CNS depression (dazed)
• Muscle twitches (fasciculations)
• Hyperexcitation
• Convulsions
• Coma

  In humans 8 different forms have been identified - in dogs there are probably 4 different types :

1. Type 1 (von Gierke's Disease) due to deficiency of glucose-6-phosphatase. Occurs in 6-12 week old puppies resulting in slow growth, hypoglycaemia, hepatomegaly (due excess glycogen) and decreased response to glucagon. Laboratory diagnosis  : increased blood concentrations of  lactate, uric acid, cholesterol, free fatty acids, and triglycerides.
2. Type II - (Pompe's disease). Caused by deficiency of lysosomal acid alpha-glucosidase. Causes excessive glycogen build-up in cardiac and skeletal muscle. This disease has been reported in mainly male Lapland dogs. Signs occur after 6 months of age and include vomiting, regurgitation, megaoesophagus, panting, muscle weakness, abnormal cardiac function. The disease is slowly progressive and affected dogs die or are euthanased by 18 months of age.
3. Type III - Functional (so called hunting-dog) hypoglycaemia. Similar to Cori's disease in humans which is caused by a deficiency of amylo-t-phosphatase. This condition affects hyperactive working dogs after 1-2 hours of exercise. They recover after a few minutes of rest, but remain exhausted. This disease  may not in fact be a glycogen-storage disease - it could be related to poor nutritional management and stress factors, including psychological, physical and environmental factors (eg high temperatures). Feeding during exercise may prevent the condition from occurring.
4. Generalised - Affects small breed puppies and juveniles. This may be a stress-related hypoglycaemia  precipitated by cold, excitement or starvation - and as yet it is not proved to be a true glycogen-storage disease.

Treatment involves the administration of glucose intravenously and nutritional management

Updated October 2013