Glycogenosis, GSDII

Glycogenosis (GSDII -  glycogen storage disease type II, Pompe disease) is  a lysosomal storage disease that has been reported in closely related  Scandinavian dog breeds:  Finnish Lapphund and Swedish Lapphund and the Lapponian herder. This disease is characterized by defects in glycogen processing leading to accumulation of glycogen in vacuoles of myocardial cells, liver cells and the cells of oesophageal smooth muscle and of cerebral cortex cells. It is caused by deficiency of a specific enzyme alpha-glycosidase active in lysosomes which is needed to breakdown glycogen to glucose in lysosomes. The clinical signs in affected dogs are very severe and include progressive muscular weakness, vomiting caused by oesophageal dilatation, heart disease, myocardial hypotrophy and condition loss. Seppälä et al. (2013) tested the candidate GAA gene and the c.2237G>A mutation that leads to creation of premature stop codon. Due to severity and progression of symptoms, death occurs before 2 years of age in affected dogs, or euthanasia is required.

GSDII is autosomal recessive inherited disease. That means the disease affects dogs with P/P (positive / positive) genotype only. The dogs with P/N (positive / negative) genotype are clinically without any symptom. They are genetically considered carriers of the disease (heterozygotes). In offspring of two heterozygous animals following genotype distribution can be expected: 25 % N/N (healthy non-carriers), 25 % P/P (affected), and 50 % N/P (healthy carriers). Because of high risk of producing affected offspring, mating of two N/P animals (carriers) can not be recommended.

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Reference:

Seppälä, E.H., Reuser, A.J., Lohi, H. : A nonsense mutation in the acid α-glucosidase gene causes Pompe disease in Finnish and Swedish Lapphunds. PLoS One 8:e56825, 2013.