Glycogen Storage Disease Type II or Pompe disease (GAA gene)

Glycogen storage disease (GSD) is a group of inherited metabolic disorders in which there is an abnormal accumulation of glycogen in body tissues. These diseases are caused by defects in enzymes necessary for the synthesis or breakdown of glycogen.

Symptoms

Symptoms of type II GSD in dogs include muscle weakness that progressively impairs movement and exercise intolerance. Dogs with Pompe disease may tire quickly and show reduced endurance during physical activities. They have respiratory distress due to glycogen accumulation in the respiratory muscles and an increased risk of respiratory infections. Heart problems such as enlarged heart (cardiomegaly) and irregular heartbeat (arrhythmias). Dysphagia or difficulty swallowing, which can lead to weight loss and malnutrition.

Disease Management

The treatment and prognosis of glycogen storage disease (GSD) in dogs vary depending on the type and severity of the condition. Genetic testing can be helpful in confirming the disease and determining the specific type of GSD. In certain cases, nutritional management and supportive therapy can help control symptoms and improve the animal's quality of life. Usually, a high-carbohydrate diet is implemented and dextrose is administered intravenously. However, in many cases, the disease progresses and puppies do not survive more than one year.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Pompe disease, also known as glycogen storage disease type II (GSD II), is a rare inherited metabolic disorder caused by a deficiency of the enzyme acid alpha-glucosidase (AGA). This enzyme is required to break down glycogen in lysosomes. The deficiency results in an abnormal accumulation of glycogen in various tissues, especially in the muscles, causing progressive muscle weakness and damage. Here we analyze the c.2237G>A variant of the GAA gene that was identified in Finnish and Swedish Lapphund dogs in the study by Seppälä et al. This variant produces a premature stop codon.

Most affected breeds

  • Finnish Lapphund
  • Lapponian Herder
  • Swedish Lapphund

Bibliography

Seppälä EH, Reuser AJ, Lohi H. A nonsense mutation in the acid α-glucosidase gene causes Pompe disease in Finnish and Swedish Lapphunds. PLoS One. 2013;8(2):e56825.

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