GM1 Gangliosidosis (Portuguese Water Dog Type)

Affected Genes: GLB1
Inheritance: Autosomal Recessive
Mutation: chr23:3754313 (canFam3): G>A
Breed(s): Portuguese Water Dog

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Common Symptoms

GM1 gangliosidosis (Portuguese water dog type) is an inherited Lysosomal Storage Disorder affecting dogs. Affected dogs typically present with symptoms of neurologic disease around 2 to 6 months of age. Dogs with GM1 gangliosidosis have insufficient activity of the Enzyme beta-galactosidase, which is responsible for breaking down specific carbohydrates in the cells. As a result, there is an accumulation of break down products such as GM1 in cells, especially cells of the brain and nervous system. Symptoms include vision loss, Nystagmus, difficulties walking, loss of balance, head tremors, abnormal bone growth and weight loss. Once an affected dog begins to show signs of the disease, the disease progression is rapid and dogs usually die by one year of age.

Testing Tips

Genetic testing of the GLB1 gene will reliably determine whether a dog is a genetic Carrier of GM1 gangliosidosis (Portuguese water dog type). GM1 gangliosidosis (Portuguese water dog type) is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the GLB1 gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups.

There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.


  • Saunders GK, Wood PA, Myers RK, Shell LG, Carithers R. GM1 gangliosidosis in Portuguese water dogs: pathologic and biochemical findings. Vet Pathol. 1988 Jul;25(4):265-9. [PubMed: 3136586]
  • Wang ZH, Zeng B, Shibuya H, Johnson GS, Alroy J, Pastores GM, Raghavan S, Kolodny EH. Isolation and characterization of the normal canine beta-galactosidase gene and its mutation in a dog model of GM1-gangliosidosis. J Inherit Metab Dis. 23 (2000) 593-606. [Not in PubMed]