Urolithiasis (Native American Indian Dog Type) is an inherited condition of the urinary system in dogs. Dogs with two copies of the associated APRT gene Mutation are predisposed to elevated levels of an insoluble compound called 2,8-dihydroxyadenine (2,8-DHA) in the urine. Increased urinary 2,8-DHA, places dogs at high risk for crystal or stone formation throughout the urinary tract including the kidneys, ureters, bladder, and/or Urethra. Dogs with this form of urolithiasis can present at nearly any age with symptoms of recurrent urinary tract inflammation, which include frequent urination, blood in the urine, and straining to urinate. They may also have loss of appetite, lethargy, weakness, vomiting and pain. Urinary stones in the bladder can cause urinary tract infections or more seriously, blockage of the urethra. In addition, blockages of urine flow at any location in the urinary tract place dogs at risk of kidney damage. Both male and female dogs can be affected, but obstruction of urine flow is more common in males due to differences in anatomy. Not all dogs with mutations in both copies of the APRT gene will have symptoms of disease, though they will have increased 2,8-DHA excretion in the urine. Feeding of a specialized diet may be helpful in preventing stones in affected dogs.
Genetic testing of the APRT gene will reliably determine whether a dog is a genetic Carrier of Urolithiasis (Native American Indian Dog Type). Urolithiasis (Native American Indian 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 APRT gene mutation. Reliable genetic testing is important for determining breeding practices. Because symptoms may not appear until adulthood, genetic testing should be performed before breeding. 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.
Furrow E, Pfeifer RJ, Osborne CA, Lulich JP. An APRT mutation is strongly associated with and likely causative for 2,8- dihydroxyadenine urolithiasis in dogs. Mol Genet Metab. 2014 Mar;111(3):399-403. doi: 10.1016/j.ymgme.2013.12.002.