Primary Hyperoxaluria

Other Names: Oxalosis I, Primary hyperoxaluria I, PH1
Affected Genes: AGXT
Inheritance: Autosomal Recessive
Mutation: chr25:50968854 (canFam3): G>A; chr25:50717729 (canFam3): G>A

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Common Symptoms

Primary Hyperoxaluria is a rare inherited metabolic disorder affecting Coton de Tulears. Primary Hyperoxaluria is characterized by a deficiency in the enzymes that break down the organic compound glyoxylate, a normal part of the metabolic process. As a result, there is an accumulation of oxalate and calcium oxalate crystals, primarily in the kidneys. Affected puppies present around 3 to 4 weeks of life with renal failure due to excessive crystal formation in the kidneys. Symptoms of acute renal failure can include inappetence, vomiting, lethargy, decreased urine production, abdominal pain, blood in the urine and death. Affected dogs die or are euthanized within the first two months of life.

Breed-Specific Information for the Coton de Tulear

The Mutation of the AGXT gene associated with primary hyperoxaluria has been identified in the Coton de Tulear. Though the exact frequency in the overall Coton de Tulear population is unknown, 8.5% out of 118 Coton de Tulears from Finland were carriers of the mutation.

Testing Tips

Genetic testing of the AGXT gene in Coton de Tulears will reliably determine whether a dog is a genetic Carrier of primary hyperoxaluria. Primary Hyperoxaluria 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 AGXT 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. Coton de Tulears 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.


  • Vidgren G, Vainio-Siukola K, Honkasalo S, Dillard K, Anttila M, Vauhkonen H. Primary hyperoxaluria in Coton de Tulear. Anim Genet. 2012 Jun; 43(3):356-61. [PubMed: 22486513]